EDIT 7: It's done. Hurrah! If you have any reason to vote negatively please comment and explain what I could possibly add to make this better.
All right, here we go. As you probably already know, this achievement is unlocked for 100% clearing every level in quickplay/adventure. In order to get a 100% clear, you must hit every blue peg before you hit the last orange peg. This is much easier said than done of course.
This guide is split into 2 parts, general concepts for 100% clears and a level-by-level guide. Please note that there are so many ways to 100% clear every level and how I did it was one of many. From now on I will be referring to 100% clears as just plain "clears."
Part 1 - General Tactics
-Choose your character wisely. There are some levels that are a very simple choice who to use. Others are not so obvious. In general, if you are having trouble deciding, go with the zen ball. It will most likely give you a free ball and eliminate a bunch of pegs. I personally steered clear of the super guide, multiball, pyramid, and flower power, but if you can use them well then by all means do so.
-Use the green peg wisely. It makes no sense to get the spooky ball when you have very few pegs left. For the most part, use your powerups early as to obtain a high multiplier faster. If you are using the zen ball, aim for a place that will either 1) clear a lot of oranges or 2) clear a difficult section of the level. You want to know what you want out of the zen ball. Think about the shot and don't waste them. You only get 2.
-Take good shots. Basically what I define as a good shot is any shot that has a chance of getting you a free ball. There is no way to clear some levels without a lot of free balls. Your first couple of shots should focus on hitting orange pegs however.
-Get to a 10x multiplier asap. Getting to a 10x early will allow you to simply hit the purple peg and 4 blue pegs for a free ball. Free balls are a necessity, as previously stated.
-Use free ball skills. This is when you hit a single peg and land the ball in the bucket. The best way to do this is to hit a peg so it bounces to the right or left to the point where the bucket is close to the wall. For example, if the peg is at the top right, shoot it head on right as the bucket is on the right. The ball should be following the bucket across and land in it when it hits the left side.
-The d-pad is your friend. If there is a peg at the bottom of the screen and you can't use the above tactic, take advantage of the d-pad. Shoot so you purposely miss but it goes straight in the bucket. Keep nudging your shot (d-pad) until you barely scrape the peg on the end and it goes right in the bucket. If you are trying to scrape the peg on the right, be sure to wait until the bucket is going right as it passes by it. You will have a better chance of it going in.
-BE SMART. If you have 2 shots left and an orange and blue, hit the blue first. Points don't matter and a cool clear isn't going to make the blue ribbon any bluer. I've had 4 shots and 4 pegs and didn't get the clear because I was being reckless. Take your time.
-Read the other 2 solutions. No seriously.
Part 2 - Level-by-Level Guide
NOTE: Starting at the bottom is always a good option. It'll get rid of the harder levels earlier.
1-1 Peggleland - Spooky/Zen Ball
You really shouldn't have any problems with this level. Just be sure to leave an orange out of the way because they are all fairly easy to hit in this level. Free balls should be easy to come by.
1-2 Slip and Slide - Spooky/Zen Ball
Another easy level. Take out the bricks first and the rest of the pegs shouldn't really pose much of a threat.
1-3 Bjorn's Gazebo - Spooky/Zen Ball
Another simple all peg level. Fun fact: Clearing the first 5 levels will also get you 5 challenges :P
1-4 Das Bucket - Spooky Ball
This is the most fun level in the entire game. Hit both green pegs on the first shot and you can end up with a high multiplier and 11-13 balls. From there just clean up any remaining pegs.
1-5 Snow Day - Spooky/Zen Ball
This level is so similar to 1-3. Follow a similar tactic here and you shouldn't have any problems.
2-1 Birdy's Crib - Spooky/Zen Ball
This level is basically 1-1 on steroids. Multiball can work well here if you prefer.
2-2 Buffalo Wings - Zen Ball
Use your zen balls to help take out the bricks, or you can take them out yourself by getting a relatively easy extreme slide. You should already be close to a 10x by then so just use the purple peg and free ball skills to finish up.
2-3 Skate Park - Zen Ball
Once again the bricks are your enemies, focus on them and the pegs should disappear as well. Use free ball skills as usual if you run low on balls. Using the purple peg method can be somewhat tougher on this level.
2-4 Spiral of Doom - Zen Ball
Use your zen balls to help take out the spiral. Oftentimes it will give you an extreme slide and 2 free balls. From there hit all the stray pegs and any bricks remaining.
2-5 Mr. Peepers - Zen Ball
The first moving peg level! Knock a hole in both outer circles in your first shot and get the zen ball if you can. Use it to take out the aforementioned moving pegs. The rest of the pegs aren't really problematic and free balls should be easy to come by.
3-1 Scarab Crunch - Zen Ball
Use your zen ball to clear a lot of the right and left side of the board. The middle should be easily cleared in a couple of shots. This is a pretty easy level to take advantage of the purple peg. Lots of point potential.
3-2 Infinite Cheese - Zen Ball
The zen ball will probably take care of the bottom half of the eye thing if you don't accidentally do so yourself. Overall, another easy level that you can get a quick multiplier and take advantage of it.
3-3 Ra Deal - Zen Ball
The top half of the eye looks annoying but you'll probably eliminate it while going for other pegs, so don't worry so much about it. The zen ball can be used to help get the bottom in one shot. Use the other one on the right and left sides.
3-4 Croco-Gator Pet - Zen Ball
This level is annoying. There are a couple of pegs that require VERY precise timing to hit. They are the ones under the bottom moving platform things. Try and hit them as early as you can, when you can bounce off others. Free ball skills don't work well so try and use the purple peg early and often.
3-5 The Fever Level - Zen Ball
I like this level. Reset until you get a zen ball first shot and it doesn't hit any of the slide at the bottom. Aim to the right and left with that zen ball and (hopefully) watch one of the best extreme slides in the game. You should have plenty of balls and a high multiplier. No problemo.
4-1 The Amoeban - Zen Ball
Use your first shot to hit the curve directly below. From there start destroying the curvy thing from the inside out. There is a lot of free ball potential to be had in this level.
4-2 The Last Flower - Zen Ball
There is a shot that can eliminate every moving peg, but it's difficult to pull off. Look on YouTube. Otherwise, the moving pegs are not your friend. They are very hard to get free balls from. Focus on a multiplier early and then start worrying about them. Use your zen balls later but be sure that they won't "normal" clear the level.
4-3 We Come in Peace - Zen Ball
So if you haven't noticed, I like the zen ball a lot in the early levels. In this case, get them early and use them to get rid of the circle things. Shoot where the moving pegs cross paths. You'll probably end up having to use free ball skills at the end.
4-4 Maid in Space - Space Blast
Wait.... this isn't the zen ball... Reset until you get the green pegs on the spinning circles. Hit them when the entire circle is there to take full advantage. For the other three, hit a hole inside. Shoot in and hope for the best really. The pegs on the sides are fairly easy to take out and will probably be almost gone by the time you've started to worry about them.
4-5 Getting the Spare - Zen Ball
I hate this level. It's nearly all bricks. Clear holes in all 3 circles on your first shot and get a zen ball if you can. Use it on whichever circle has the purple peg, right or left. If the purple peg is in the center circle then don't worry about it. Free ball skills and purple peg free balls are both hard to do. If this level frustrates you as much as it did me, then come back to it. It belongs in a later stage in my opinion. (Possible Peggle Nights reference in the name maybe?)
5-1 Pearl Clam - Flippers
Some levels are just made for certain powers and this is one of them. Get the flippers on the first shot and try to eliminate the top 2 rows of the clam thing. The ball should always roll right back to your flippers and should make it very easy to do this. Use your next couple of shots to raise your multiplier and you should really be good to go. You may have to use the d-pad to nudge some of the pegs on the bottom.
5-2 Insane Aquarium - Zen Ball
Another easy all peg level, with a twist! You can hit the fish and it'll move to the other side... Honestly there shouldn't be much to worry about here other than the fish blocking your path. You can always hit the fish and get a total miss and hope for a free ball if you have no other option.
5-3 Tasty Waves - Zen Ball
The only annoying part about this level is the moving pegs, but most of them should get hit if you aim for the top pegs first. Just use the same basic strategy as in other levels: rack up a high multiplier quickly and start taking out the pegs 5 at a time. This level shouldn't be very problematic.
5-4 Our Favorite Eel - Zen Ball
Another easy level that has really nothing to worry about. No moving pegs and the bricks are all easily taken care of with a few good shots. Free ball skills should clear the level in the end.
5-5 Love Story - Zen Ball
I personally dislike this level. Try and knock a hole into each of the fishes' eyes on your first couple of shots. Then try to get most of them later. The pyramid has a pretty good outside wall, which makes the flippers a good second option here, but I found the ball always went too far inside too quickly for them to be worth the while.
6-1 Waves - Spooky Ball
Now you aren't always going to get a great shot with the spooky ball here, but this level isn't that hard anyway. Your first shot will most likely roll into one of the slopes and down all the way... but if you can pull it off you can try to make the ball slide over the whole top slope. Overall, an easy level though.
6-2 Spiderweb - Spooky/Zen Ball
The spooky ball works great if you can use it early. But the zen ball can get a great shot pretty easily on this level. The choice is yours. Try not to forget about the pegs on the very edges as they can be somewhat hard to see. Free ball skills work perfectly here too, assuming you don't leave too many pegs at the end.
6-3 Blockers - Spooky/Zen Ball
I like the spooky ball on the levels that are meant to use it... Anyway, the one annoyance with this level is that some of the pegs are barely hittable because of the blocker things getting in the way, and free ball skills are harder to do. Focus on eliminating those hard-to-hit pegs early on when you have more pegs to hit off of. Other than that, there isn't much else I can tell you.
6-4 Baseball - Spooky Ball
Take your first shot outside the wall of blues and try to raise your multiplier quickly. If you get the spooky ball it will help even more. Playing the level like normal should be enough to get you close to the clear anyway. Simply use free ball skills in the end and the purple peg wisely like on most other levels. Nothing new here.
6-5 Vermin - Zen Ball
Bricks... bricks are bad. But there is a solution! Your first couple of shots should be focused on taking out the top right and top left structure things. Do not get the zen ball yet. Punch a hole into the big middle circle and then get the zen ball. Aim inside, and hopefully it will give you a big extreme slide that will take out most of the circle. This can be kind of hard to set up, and the level is very possible to complete other ways, but if you are desperate try to set up a situation like this. It'll help.
7-1 Holland Oats - Zen Ball
This level shouldn't pose much of a threat compared to what's coming up. Just focus on taking care of the windmills early, use your zen balls wisely, and use free ball skills in the end. Not very problematic.
7-2 I Heart Flowers - Zen Ball
I do not heart flowers.... this level is annoying. Try to get into the flowers and get a small slide going there. The ball should fall and hit some of the stem. I honestly don't know what else to tell you. This is a level that there is no real strategy to. If you've gotten this far you should have some ideas of your own. Try them out.
7-3 Workin From Home - Zen Ball
This level is extemely annoying and was one of the ones I spent the longest time on. The hardest part is getting the pegs inside the moving circles. I highly recommend using the zen ball to hit them. It should get most of them leaving you with just the edges of the river to contend with. Practice makes perfect, especially with this level.
7-4 Tula's Ride - Zen Ball
All of Tula's levels are extremely annoying to clear, and this is possibly the most annoying. Don't move your aim for the first shot. It should bounce left and eventually down and out. If it hits some of the "road" then consider that a bonus. Shoot the next ball so goes underneath the front of the car, slides back, and takes out the first row of flat pegs. From there start working on the right side of the car, preferably from the inside out. You should have most of the road cleared by the time most of the car is cleared, and lastly work on the wheels. Shoot a ball in there and it should hit most if not all of the pegs. Free ball skills are nearly worthless here and I recommend just using the purple peg. And yes this level does deserve a long guide.
7-5 70 and Sunny - Zen Ball
The best thing you can do on this level is just slide the ball straight into the bucket for easy free balls, and really that's the only thing you can do. High scores are very hard to get, so use the zen balls to try and get rid of orange pegs early. Another trial and error level...
8-1 Win a Monkey - Zen Ball
Get the zen ball on your first shot but DO NOT hit the mouth of the monkey at all. Then aim toward the inside of the ears (off the top of the 3 normal pegs) and hopefully the zen ball will eliminate most (if not all) of the mouth, leaving you with not nearly as much to contend with. The eyes can be taken out very quickly, just leaving you with a few stray pegs and bricks. Just don't be stupid and you should be able to get the clear.
8-2 Dog Pinball - Zen Ball
As usual, opening up the circles will allow you to get a shot in there and take care of most of those pegs. The ears can be taken care of by a good bounce off the wall, or by the zen ball. You shouldn't have too many problems here, and there aren't that many great strategies to pull off.
8-3 Spin Again - Zen Ball
For the circles on the edge, punch a hole in them and then get another shot inside. The ball should stay at the bottom and get rid of the whole circle. Use the zen balls on the middle of the level as the moving bricks can be hard to take out.
8-4 Roll 'Em - Zen Ball
You can take the first few shots without moving the cursor and set them up so you get a free ball each time. From there start trying to get a higher multiplier and get inside the dice. This level is difficult to clear so I highly recommend taking your time on it. Use the purple peg in the end because you should still have a lot of bunched up pegs.
8-5 Five of a Kind - Zen Ball
Another very annoying level. Try to take care of the tops of the cards so you can just keep shooting balls inside. Get a high multipler as fast as you can and start using the purple peg. It is extemely easy to get the 5 necessary pegs for a free ball if you still have some of the edges of the cards remaining. Use that to your advantage.
9-1 The Love Moat - Zen Ball
This level isn't really all that bad. By now you should be good enough to know to just try and get rid of the bricks first. Since the infinity symbol things are circular-ish, shooting balls inside them is always a good way to start. The outside pegs aren't problems at all, as free ball skills work well. Fireball is also a good backup if you can't get it with the zen ball.
9-2 Doom With a View - Zen Ball
Your first shot should hit the edge of the right curve thing and bounce over to hit the left curve thing. Then it'll slide on the middle thing and hopefully end up in the bucket. From there bounce your ball off the top of one of the vertical bricks on either side. It should hit a lot of pegs inside the curve thing. Ideally you should do this with the zen ball for both sides, but this may not be possible depending on your layout. You should be pretty much good to go from here. Free ball skills are super easy to pull off.
9-3 Rhombi - Fireball
Get a fireball as soon as you can. Use it to take out the rhombus that either has the other green peg or more orange pegs. Then use the other fireball to take out the other rhombus. It's unlikely that you'll hit every brick, so try to get rid of the rest as soon as you can. From there it's just scattered pegs, which shouldn't be too problematic.
9-4 9 Luft Balloons - Zen Ball
This level is pretty easy because the zen ball will do a lot of damage to it. Just try and hit holes into each of the balloons for it to be able to do so. If you can get a high multiplier quickly, it's pretty easy to take advantage of the purple peg as all the pegs are really clumped together.
9-5 Twisted Sisters - Fireball
Honestly just use the same concept for the level as you used for Rhombi. The only real difference is that the bricks are pegs and the left one is higher up. It can be harder to use the fireball effectively on the left one, but it should be significant enough to make a good enough dent to get you on your way.
10-1 Spin Cycle - Zen Ball
The very first thing you should notice is that the pegs directly under the spinning thing are nigh impossible to hit on a direct shot (bouncing off the wall may just nudge it). So your priority from the very beginning is to get rid of those right away. The spinning thing can be annoying. It'll often send your ball on a totally different shot than you wanted. Just try and be careful and take your time to not screw up. The purple peg works well because free ball skills can easily get screwed up.
10-2 The Dude Abides - Zen Ball
Your first shot here is very important. You want to hit a 1-2 brick wide hole in the outer ring, and and try to hit no other peg on that ring. It's not as hard as it sounds. Just shoot to the right. From there, as the hole is coming around toward the top, aim inside to the left, bouncing off the second ring. It should slide on the first ring for an amazing extreme slide. Use this tactic for each subsequent ring and you shouldn't be left with much to work with. Start using free ball skills only once you have nothing in the middle for the ball to hit.
10-3 When Pigs Fly - Zen Ball
The peg on the top right, to the left of the beehive (where the ball comes out of the warp), cannot be directly targeted at all. Focus on getting rid of it early. Otherwise, the warps can be annoying because they block your shots and free ball skills. Try and use the purple peg a lot for this level.
10-4 Yang, Yin - Fireball
The fireball is, without a doubt, the best powerup to use for this level. Restart until you get a green peg on the left side of the level, which is where you shall begin. Poke a hole in with your first shot then try and take a good second shot in there. Next, get the fireball. Aim directly down the right side of the right yinyang thing. It should hit the wall, following the edge the entire time. Bounce it off the bucket and you stand a pretty good chance a a free ball too. The second fireball isn't near as important, but the left side of the right yinyang is a good place to go to if it's still there. There are a lot of pegs in this level, so take your time. Take smart shots, get that multiplier up, and rejoice. This is the 6th hardest level in my opinion, but for some it can be higher.
10-5 Zen Frog - FLIPPERS
And when I say flippers... I mean it. This is the 2nd hardest level, so skip it and come back to it if you want. Your first shot is extremely important. What you need to do is hit the green peg and get the ball on the outside of either helix. I generally chose the helix with more oranges. Make sure you haven't hit a single peg on the other helix. From there, continue to use the flippers to hit nearly every peg in the helix, except maybe a few on the top. Repeat for the other helix. If you manage to pull it off, you're good to go. The rest is simple. This will probably take you a bunch of tries though, so just be patient. You'll get lucky eventually.
11-1 Paw Reader - Zen Ball
For terms of how I'm describing the level, spiral 1 is the one that is directly down from where you shoot, and it goes clockwise up to 12. Hit the top peg on spiral 3 and try to bounce it in between spiral 1 and 2. From there, shoot the ball so you get a perfect slide on spiral 4. You may end up hitting some pegs on spiral 6. I honestly don't have any tips from there. Use the Zen Ball wisely and hope for luck. Free ball skills are really the only way to get free balls too other than the Zen Ball.
11-2 End of Time - Zen Ball/Electrobolt
If you have the Peggle Nights DLC and have unlocked Marina, this is probably the only level from the original game that acutally suits her. Just hit a top peg and you should get the rest in the row if you timed it right. Otherwise, the Zen Ball is the way to go. Your first focus is the right side simply because it's easier. You want to hit the corner of the top pegs in rows 2 and 3 so it bounces up, hits the top, and bounces perfectly down to give you an extreme slide. Sound hard? It isn't. If you can time it so that you get a free ball, that's even better. Continue to clear out the right side as much as you can. Rows 4-6 are tough to get a great shot on, so that is a good place to use the Zen Ball if you're struggling with them. Begin to focus on the left when a good majority of the right is gone. Try and punch holes in the middle of the rows so you can bounce off the top of the pegs to get the ball to slide down. Another option is eliminating the right side completely. You can simply use free ball skills until you clear out the entire left. The only problem I've found is that you have very small room for error. Just be careful.
11-3 Billions & Billions - Zen Ball
The hardest level. It took me an hour and a half of trying to get it (by comparison I got ~30 levels done in around 3 hours). The first thing you need to know is that you can't directly aim at any peg below the slants... except the ones directly below where you shoot. So don't touch that dial, take 4 shots from the beginning without moving anything. The ball will follow the same path each time, so memorize when to shoot so that you will always get a free ball. These 4 shots serve a dual purpose. First, they allow you to get rid of some pegs for free. And second, they get rid of the middle. You want the ball to come out of the UFO and hit the pegs on the sides, not in the middle where you can somewhat aim. Be absolutely sure you have an orange peg up top to hit in the end. Odds are you'll have 1 shot left so you don't want to risk missing a bunch and hoping for free balls. Free ball skills are completely worthless and so is the purple peg. Just persist and you will conquer.
11-4 Don't Panic - Zen Ball
Your first and most important goal in this level is to hit the pegs that aren't directly hittable. This includes the pegs in the top right, top left, and directly below the yinyang. I have never managed to hit them by bouncing off the yy no matter how precise I've gotten. The solution? Use the other pegs and bounce off them. Avoid the Zen Ball for a little bit. Make sure you have hit the top left and top right pegs before getting it. Oftentimes it'll take away your only options that allow you to get your shot up there. The Zen Ball will normally hit under the yy so that should help you a lot. In the end, this level isn't really that bad, it's all about hitting what you can't aim at.
11-5 Beyond Reason - Zen Ball
If you have done the 750k challenge you should know what to do here. Get rid of some of the pegs on the left or right of the helix so you have room to bounce off the wall. Time your shots to poke a hole in the bottom of the helix. Get the Zen Ball. Aim for the wall again. The ball should get right into the bottom of the helix, be carried up and hit every peg except maybe some of the bottom ones. Clean up the sides and you should be good to go!
3 Quick Things:
1) These are just some basic strategies. There is always another way.
2) I probably didn't even use these exactly both times I did this achievement (iPod and 360). It took me 4 months the first time and 2 weeks the second. You'll begin to see what works and what doesn't after a few tries on each level.
3) Good luck!!!!!!!!!!