These methods are tried, tested and proven. Good luck to everyone trying to conquer this legit; it's certainly not impossible, but finding others who have the skill and patience is the most difficult part. If you can't find a team, it can be done with some skill and some luck in the Gib Fest
or Last Man on Earth
mutations. See a guide for Gib Fest (how I got the toughest ones done) at the bottom.
Update 12/30/09: There is a glitch you could use instead; however, this guide is for those seeking to legitimately acquire the achievement. If you're looking for that type of solution, please look elsewhere.
• Turn on full captions. (Options -> Audio/Visual -> Subtitles (Full Captions)
• Watch the Developer Commentary from L4D1 and L4D2, the developers provide valuable insight into how the enemies are generated, when, where and why. Know your enemy! Keynote from L4D1 for those who don't have it: the game punishes poor behavior, it punishes you if you disobey it's rules like splitting up or not shutting doors behind you. It will spawn infected in harsh ways to remind you. Follow this guide and you'll hopefully not be at it's mercy. http://www.youtube.com/results?search_query=l4d1+developer+c...
• 5.1 surround sound. You simply are at a tremendous disadvantage without it. I suggest either a quality pair of 5.1 headphones or a full speaker set-up for playing L4D on Expert.
• Do some initial campaign play-throughs, preferably with your team, and preferably on Advanced. Learn the maps, learn the fast routes, learn where the items spawn.
• Your teammates should never be farther than ~20 feet from you. All of them. Never. If you can't keep the team together you can't survive. If one person goes back to help someone every person goes back to help that person, even if there isn't a zombie in sight. Never split up! The game is called Left FOUR Dead, not Left 2&2 Dead, not Left EveryMan4Himself Dead, but Left 4 Dead. You do not have 100 hit points, you have 400 hit points, protect all of them!
• Do not friendly fire. Use melee (LT) when there's any doubt. Learn how to shoot around your teammates, always duck when you shoot (unless you're in danger) for greater accuracy, and stop shooting when there's a slim chance someone may step in front of you. Don't run around when people are shooting, especially if they're shooting at something near you. This is a game of skill, and it will require practice.
• Carry adrenaline and pipe bombs, and only use them during crescendo events and tank encounters, or when you have access to more. Resist all other urges or you will surely be at a loss when you most need it. Molotovs are good for throwing behind you in tunnels and tight corridors, and pills are good for long-term HP boosts. Unlike the first L4D, popping pills is now something you can do more liberally while looking out for adrenaline shots.
• Watch your back! Constantly be looking around and know what's behind you, all the time, no matter what's in front of you. The healthiest in your group should be point, and the second healthiest should watch the group's back. Point should always be crouching so people can shoot over them. The other two should be watching for special infected on rooftops, in shadows, and killing zombies.
• Your group is as good as it's weakest member. Keep health distributed as evenly as possible. A defibrillator is far more valuable to the team than a health pack, and is far more rare. Pick it up if you come across it, even if you have to ditch a health pack.
• If you are using a shotgun, aim outwards when shooting infected off your friends so they don't get hit by the spread, and reload as often as possible - you can reload and melee at the same time if you mash the reload button.
• Forget the melee weapons, they're fantastic for crescendo events but not much else, and finding pistols isn't always easy. If one person wants to carry a melee weapon and play point it may be helpful, but it may also cause a lot of problems. Do you really want to run out of bullets and have to fight a tank with a guitar on Expert? Pick up the pistols and learn to use them. Use the pistols 90% of the time, and shoot for the head. Save your main weapon for special infected, dense hordes, and tanks. The big exception to this rule is the chainsaw, as it shreds through even tougher enemies with one swipe, and when it depletes you get your pistol back. The other exception is in tunnels, like the Tunnel of Love, where fighting is in close-quarters for a very long time. Thirty pistol bullets can take down a smoker or charger that has one of your friends from a good length away when there's no time to chase it down with a katana. Players running around with melee weapons are also harder to shoot around. Melee weapons are for crescendo events and tunnels.
• The M16 and auto-shotgun are the two most powerful weapons, and the SMG is almost always a better bet for accuracy than the cheap shotgun. The hunting rifle is a niche weapon that few will find easy to use, so unless that's your particular weapon of choice, I would suggest not to bother. Again, by using the pistols you can conserve ammo and keep your favorite firearm around longer, as well as any upgrades.
• Laser-sights! Get them and keep them. They make your weapon more accurate, and more importantly, let your teammates know where not to stand. Fire ammo on an M16 is also highly effective.
• There's a lot of points in the maps that you can't turn back from, usually a short jump down with no way back up or over. One person should go ahead and the other three should wait until it's clear for the entire group to move at once.
• Don't go backwards, always be moving forwards (or at least sideways). Don't go wandering looking for items, even as a group, if it requires you to backtrack more than a few dozen feet. If it's not on the way, it's out of the way. If you're running low on supplies, particularly health and health kits, it's good to break to check any nearby and upcoming rooms, even if, and especially if, you're near a safehouse. It's far better to risk searching for items near the end of an act than it is to get stuck in the next one without any. This is the only real time it benefits the team to split up, keep the healthiest survivor in the safehouse while the other three scavenge before the next act.
When you hear the music, kill everything in the area without moving forward, take cover and heal up if you're below 50 or take an adrenaline shot, this way you can run as fast as the tank. If you can't run as fast as him then he will almost certainly kill you. Everyone should move to the closest open area void of cars and spread out and run in lap-like circles (not necessarily in the same direction, just always away from the tank), strafing and shooting, follow the same path so you don't get stuck on geometry and shoot as much as possible. If you can't get to an open area, then use the world geometry, jump over tables and small fences, as the Tank will be slow to work around them, and shoot while he does so. Getting a tank to duck under something will make him slow and vulnerable. Watch for the occasional special infected spawns, if someone gets snared by a special infected, help them before going back to shooting the tank. Stop shooting and watch where you're running if you're near boxes or debris. Lighting the tank on fire is helpful for depleting his health, but is not necessary, and in certain situations is a waste of a molotov. If someone does go down, use adrenaline or kill the tank before you help them up, but always shoot any zombies off them so they can focus their fire while they're on the ground towards the tank.
Handy weapon chart: Hordes
When it's [Incoming Attack] time, get against a wall, then lay into the horde with the pistols, if there's no time to reload or the shots didn't land and the horde is closer, switch to your main weapon and blast away... but reload your gun before going back to your pistols. When the zombies get close, shove them back, and when there's a few moments to think do a quick horizon check for any special infected before going back to blasting incoming zombies.Special Infected
Special infected do the most damage. Witches can be avoided, and Tanks automatically get everyone's attention, but the special infected that pick you out of your group during the hordes brings your HP down the most. Use the captions to identify the presence of various special infected and don't let them split you up. If your teammates are carrying pistols, they'll have to learn to crouch and shoot the infected without shooting you, and it seems this is one crucial point that most don't seem to grasp.
When your friend gets tackled by a special infected, your reaction should be to shove away anything close to you, crouch, turn towards your downed teammate, switch to your non-active weapon (so you're working with a full clip), and shoot the infected. As soon as it's dead, instead of going back to defending the group, shove the zombies back again and then the group works it's way to the person who got snared (who will no doubt be making every effort possible to rejoin the group), since they are still highly vulnerable. Many times people will frustratingly try to run over to shove the enemy off while it shreds 90 HP off; or worse, shoot the enemy off and then consider the situation resolved and go back to defending themselves, leaving you to get vomited on and pounced again, only to find you completely dead when next he turns to look. When the team is split up the main focus is always to reunite it, and the special infected are designed to divide the team.
Certain special infected can be ignored to some extent, especially the boomer, in any area you can make good time through, and they'll prevent new ones from spawning while they helplessly try to catch up. This is helpful if you're in a clearing and can make rapid forward progress, but be sure to keep tabs on where they are after you pass them. That's not to say new ones won't spawn, but that the existing ones already placed on the map won't be replaced until they commit suicide (which they eventually do when you get too far away). Smokers and spitters, on the other hand, should always be killed. The purpose of doing this is to continue making forward momentum when common infected are scarce, as chasing a jockey around a bush for 45 seconds just gives the Director more time to spawn in new infected... this does not mean you should leave any potential threats alive.
-------------------------------------------------------------------------Campaign StrategiesDead Center
Act 3 is the toughest spot, because of the alarm event, so don't waste all your bombs at the gun store getting the cola. Take it slow, hug the left wall right out of the safehouse and through the mall. When you get to the windows, make sure you've got some boomer bile and pipe bombs and everyone knows the exact path to the alarm shut-off. Running left, up the stairs, then left again is the fastest route. If you're having a lot of trouble here, turn up your brightness setting, it will help a lot.
Getting the gas in the finale will not be easy, but if you're fast and organized you can get it done while fighting the first tank. You'll want to stay together and head up the stairs at the far end of the mall to start and throw down the gas cans to the lower level, preferably on the info center roof. The tank shows up, and you should be heading up the second flight of stairs to throw down the remaining canisters and take the shortcut through the boards to escape. Of course, the entire time, you'll have to be weakening the Tank with bullets and fire. Kill all spitters before dealing with gas canisters!Dark Carnival
The roller coaster is no exception to the rules, if one person gets smoked or jockeyed off the ledge, everyone follows. The harder part here is in act 4, the gauntlet run to the stadium... you're going to need four pipe bombs or puke jars (or three and a molotov) for this section, adrenaline, and fast melee weapons, and if possible a chainsaw. When the gates open, toss the first bomb at the opposite end and the second one at the gates (just after you all get through - a molotov will work here, as well), then use the adrenaline and shoot the zombies in your path as you run. Before those bombs explode, throw a third, and before that explodes, the fourth. This may very well be the hardest part of the game, so good luck, and stay together! If someone goes down before the end of the initial corridor to the stadium, help them up, at any point after that it's crucial to just go.
The finale here is real easy since there's enough fireworks and gas cans to take out the entire horde army if you place them correctly.Swamp Fever
Doesn't seem to be any specific trouble areas here, just stick to the tactics and stay out of the water as much as possible. Stay in the middle of the plane, watch for spitters, and take turns taking the outsides. Be wary of the mud men and getting pulled off the walkways by smokers or jockeys, but stay above to avoid the other infected and keep a clear view. Know your route, stay grouped, and get to the boat.
For the final act you're going to want to group up in a room and stand back from the entrances shooting, then when the tank comes you're going to have to scatter and hope you don't get dragged away by a smoker, but it's best to keep the tank inside the house, continuously going up the stairs, out a window, then back up the stairs, or alternatively, get him outside in front of the garden and run in circles. As soon as the tank is dead get to the opposite end of the garden and defend. This is just like Blood Harvest from L4D1 with an extra Tank thrown in the mix.Hard Rain
This might be one of the easiest campaigns due to the stealth nature of it. Learn the map and you can really cruise straight through some of the sections without a whole lot of effort. The wide-open areas make it difficult for the infected to sneak up on you, but when the storm hits you'll want to get indoors. Save your pipe bombs and boomer bile for the two trips through the field and it shouldn't be too difficult.
There's some nice alcoves in the burger restaurant kitchen, and when the tank comes, have two people stand by the exit in the back by the kitchen (that's their escape route), and two people circle the tank jumping on tables while everyone shoots. If the tank goes into the kitchen the other two should go around to the other back entrance and try to get the tank back in the restaurant.
Wait out just behind the restaurant for 30 seconds or so after the second tank dies, one person should face towards the inside of the restaurant, the other three should observe outside between the restaurant and boat. Before taking off for the boat, try to locate the tank and toss a boomer bile at it to slow it down, as it takes a few moments to get to the boat and standing near the water's edge (or even on the boat) is dangerous.The Parish
Also not very difficult, but one of the longest campaigns. In the first crescendo event, as soon as the alarm is turned off, group up on the ground just below, do not stay at the top as there is no cover. Again, pipe bombs and adrenaline will get you through the crescendo event before the cemetery, and again the same strategy will get you across the bridge to the evacuation chopper. Try to find as much adrenaline for the bridge run as you can in Act 4. When going over the bridge, hang FAR left around the trucks from the very start. Stay on the low road, as well, and when the tank spawns, hit up the wooden walkways on the left to dash around it. Make sure you climb up the oil tanker when it cuts you off from running on the left side, and then right onto the off-ramp and you've done it! Certainly the easiest finale event.
Gib Fest is a mutation, it requires internet access and the first DLC and is only active when Valve puts it in the rotation.
In Gib Fest you get a magnum and an LMG and infinite ammo. The biggest benefit here is to the AI behavior, as they now shoot liberally with their main weapon and basically mow down hordes with ease. If you're having a hard time assembling a full team of dedicated players for any campaign, Gib Fest is the way to do it solo.
The strategy is fairly obvious for the most part, but things are still going to get dicey in the crescendo and finale events and you're still going to have to have some skill and practice to get it done. The same strategy applies.
That's it. Do not get frustrated, this is a very challenging game and requires practice and skill. Do not make the same mistakes over and over. If one strategy is not working, try a different one. If you get stuck for an hour on the same part, turn down the difficulty to Advanced and get some practice with the team and try it again later. Most people are not pleasant when they're frustrated, so take it easy, mute your mic if you need to vent, and remember that it's probably a 3+ hour commitment to finish a campaign and you don't always get it on the first try.