You can run this on Normal with just a few easy skulls on, as long as you stay under or very close to par time. Once you hit the 15:00 mark, your score will start to drop - FAST. You will need a score of 25,000. To keep track of what your score is during the level - with the time multiplier applied - switch to competitive score under options before you begin.
You will want to be familiar with this level. Know where enemies spawn. The idea of this is to take out enemies as fast as possible and move on to the next area. Know where you can find more BR ammo and know where heavy weapons are.
Getting kills without dying builds up your killstreak and earns you more points. Multikills also give you slightly more points.
Angry - enemies fire faster and more frequently. No big deal, really.
Famine - Weapons dropped by AI have half ammo. Normally you would want to pack a plasma pistol, but elites go down fast enough on normal.
Fog - No motion tracker. Not necessary if you know where enemies spawn.
Iron - Dying restarts the level. On higher difficulties this would be annoying, but as long as you pay attention to your shields, you won't have trouble staying alive. Normally you can save and quit to avoid the iron penalty but you can't afford to end your killstreak.
That's Just...Wrong - Increased enemy awareness of you. Not a threat on Normal.
I opted out of using Thunderstorm because Ultras take too long to kill and we're going for speed. I didn't use the Catch skull because often the grunts would stick each other by accident and rob you of points. Also, a well placed grenade will force you into restarting the level.
-Screw your AI allies. If they get the kill, no points for you! Killing them will take away about 100 points, but they'll likely steal more than that from you.
-If you feel like an enemy is taking too long to kill, skip them. It's not worth a minute taking out that elite on a ghost.
-Get those phantom turrets. Easy points.
The first part of the level has a good kill per minute ratio. Stick around and don't skip it using the rooftop trick. Take out some of your marines with a grenade so they don't jack your kills later. Eliminate enemies as fast as you can. When the drones show up, use that turret and maybe nab a killionare. When the phantom comes to drop off enemies, shoot the phantom's three turrets with your own. Each one is worth about 250. The two hunters coming through the door are worth big points. Again, utilize that turret. If you need ammo for your BR in this area, there's some by the turret and some on the same floor near a dead marine in the back. And maybe there's some on those marines you
killed, you murderer.
Make your way through the alleys fast and precise. Picking up a beam rifle to do some counter-sniping isn't a bad idea.
Once you get to the part with a warthog, another phantom will drop off enemies. If you can get those turrets again, go for it. Forget the warthog, and go for the elite in a ghost that shows up down the street. If you can't hijack his ghost, there's one by the downed pelican on the beach, along with some enemies. You might want to kill those marines because they will stay in the warthog and steal your elite kills.
If you're pressed for time, you may want to focus on killing just the elites along the beach. Again, the phantom that shows up will give you a good amount of points if you can take out the turrets.
Before you enter the tunnel, there's a building on the beach with a sniper and rocket launcher on the roof. Same building with the terminal. Use the rockets to take out ghosts easily. Snipe the jackal and take out the elites that drop.
The tunnel takes about 3 minutes to rush through.
I had about 27000 score at the 15 minute mark, and finished at 15:51 with 25400 score. Score drops at a fast rate after the par time. If you're at 25000 or more and you can make it to the end before 15:00, you're good.
In the tunnel, you can get some kills with little time loss by splattering enemies. You might want to stop and get the elites if you still need points. I shot at the covenant transport vehicles until at least the elite on the turret died, because my ghost was beat up and I was afraid they would kill me. This took quite a bit of time, though, and nearly cost me.
Depending on your familiarity with the level, you may need to practice this a few times to learn enemy spawns. At the beginning of the level, being able to wipe out the enemy when they spawn grouped together will save you time. Know where the jackal snipers are perched in the alleys, so you can quickly pop them with the BR and move on.