Cairo Station

Wait to the side of the door. As soon as you see enemies on your radar, you can start moving. Try to get duel plasma rifles as fast as possible because they kill enemies quick and they don't need reloading. After clearing the first room, look at the Malta. Looking at it makes it blow up faster and saves time. Do the same thing in the next room with the Athens. Take master Gun's shotgun after the elites kill him. This will make the bomb room go faster. When you get to the part with the bugs, bounce a nade off of the slope so that you can kill some of them as they are flying up. The door at the bottom won't open unless 4 or 5 of the bugs are dead, so shoot them as you are going down if you didnt kill enough.

Outskirts

Grenade jump above the map at the start. If you have trouble with that, you can jump off the lights in the hallway. Then run straight to hotel Zanzibar. Pick up the magnum and waste all of its ammo. Having a gun with empty ammo prevents you from carrying over weapons to Metropolis. This is good because on metropolis the game will give you 4 more grenades. Then just drive through the rest of the level. If you are have trouble squeezing between the wall and this shipping container. You want to try to get your right wing in first. This is done by going slightly to the right and then tapping 'A' to raise the front right as you get there.

Metropolis

Grab the warthog at the start and drive through the whole level. Once you get to the wraiths, board the wraith and throw a grenade at the exact same time. This puts the grenade inside of the wraith and kills the driver almost instantly. Then use the wraith to kill the other wraith and the phantom that drops off enemies. Using the setup in this video: http://www.youtube.com/watch?v=q76vCjF431A , grenade jump onto the scarab early. You want to line up with the corner and then throw a grenade as Sgt Banks pausing between saying, "I dont think its stopping" and "Get your head down". If you are having trouble with the trick, it only saves like 10 seconds, so boarding the scarab the intended way isnt too far out of the way. Sometimes the scarab will disappear. If this happens there is nothing that oyu can do to finish the level. I am not sure exactly what causes it, but Im pretty sure that it is caused by killing the 2 wraiths and the phantom too quickly.

Arbiter

Run straight forward and then stick the elite that is messing with the control panel. This causes the door to open immediately. Then stick the elite with the sniper and steal his sniper. After that, snipe the two grunts closest to the door. Killing all of these allies skips a lot of dialogue when waiting in the room. It causes the door to open much faster. Run through the rest of the level until you get to the elevator. It is possible to hit the switch to start the elevator through the wall by jumping and crouching at the middle of the wall. After riding the elevator, quickly push the button at the end of the room and then kill all of the enemies. After everything is dead a couple Fuel rod gun- wielding grunts will spawn. Kill those and then the door at the other end of the room will open. Then just run through the rest of the level. When you get to the part of the level where the Heretic flies off in a banshee, stand behind the block that is next to the door on the right (if you are looking at the glass) then look at the door on the left. This increases the chances that the door next to you will open. Finally get a banshee and fly up and to the right at about a 45 degree angle and you can skip the phantom escort mission.

Oracle

At the beginning of the level, jump above the room so that you can kill the infection form flood quicker. They will spawn in the vents or in the central box thing. After killing a certain amount, the door will open and you can continue to the elevator.
Once on the elevator, just kill enemies until the sentinels spawn. Once that wave of enemies is dead and the elevator starts to move again, you can drop down to the ledge below. You cannot drop earlier because there is a death barrier that is moving with the elevator. Then kill all the flood in the next room. The next wave of enemies at the start wont spawn until you kill all 4 carrier forms and the flood that get brought back to life. Make your way through the rest of the level as normal until you see the heretic running toward the door. Kill all the sentinels and the flood in this room to trigger the cutscene. Then ride the elevator up and cut the cables. After cutting the 3 cables, it is possible to sword cancel through the middle of the large room. This saves time and looks really cool. Then fly the banshee and make your way to the heretic fight. When fighting the Heretic, the first two that you see to your right and left are clones. The real one flies over the seraph. Once you kill him the level will end.

Delta Halo

Grab the ODST's BR (optional grab a plasma pistol) and make your way above the map. Go to where the jackal snipers spawn. Drop down on the slanted slope to spawn them and then continue above the map. Drop in and grab a ghost. You can either grenade jump across the waterfall doing the double grenade glitch or you can hit the button through the wall to lower the bridge. To do the double grenade glitch, over charge a plasma pistol and then quickly press L twice as soon as the gun is half way done over heating. This will throw to grenades at once. The launch is a little difficult, but it saves about 30 seconds. You must hit the a loadzone/checkpoint next to the waterfall to continue with the level. If you launch too far to the right, go backwards to hit the trigger. Continue on the ghost until the "You break it you buy it" chapter. Then you want to take the ghost into the structure to spawn the enemy ghosts and then double back to get above the map. Spawning the enemies is necessary to beat the level. After taking the ghost above the map, drop the edge of the ghost into the "Off the Jackal..." chapter to load that section. Continue above the map for the rest of the level with the ghost and drop in at the end of the grassy hallway. If you fall into the "Off the Jackal..." chapter, it isnt a big deal, just take the ghost through the rest of the level. Kill the honor guard elites and grab one of their swords before the level ends. This will be used to swordfly in the next level. Even if you cant swordfly, it is still helpful to have for sword cancels.

Regret

At the start of the level. Sword fly to the jackal sniper that is at the other tower to your right. Sometimes he is not there and you will either need to throw a grenade to lure him out or revert to last checkpoint. After getting there, jump onto the gondola. Stand at the edge of the ledge that separates the gondola from the center portion of the map to spawn the enemies. As soon as they spawn, quickly run and jump onto the gondola. Another way to do this is to swordfly to the center structure and then sword cancel off of an enemy onto the moving gondola. After the moving gondola crosses paths with the other gondola, jump onto the other one and press the switch. This will spawn some bugs and 2 elites on the gondola that you jumped from. Kill them to continue with the level. Some bugs will fly from the start of the level that you should kill too. Then ride the gondola until it is close enough to swordfly off of a jackal at the next tower. Once at the next tower. Throw a grenade at the shielded jackals and  quickly jump above the room to the cubby where the drones would normally spawn. Standing in their spawn prevents them from spawning. After all of the jackals are dead the elevator will rise. Continue through the rest of the level like normal. All the way until the gondola before regret. When you are on that gondola, first kill the banshees with the rockets and then shoot the remaining rockets at the approaching gondola. You want to kill those enemies as fast as possible. Then either finish out the gondola ride or swordfly to regrets tower and kill regret normally. Do not do the grenade-board trick because it doesnt kill him.

Sacred Icon

This level is very simple. Grab 2 plasma rifles at the start and use them to trigger the pistons that you need to drop through. The pattern for the direction that you need to look after the piston opens is. Straight-Left-Right-Left-Right. After getting to the large room, activate the 4 pistons and then press the button. It is not necessary to kill the first enforcer, he will die as soon as the elevator starts to move. When the big door opens. Use the carbine to take off the legs of the second enforcer and then stick it a couple times to kill it quickly. After it dies, immediately stand next to the door that will open. Continue on with the rest of the level as normal. Kill the waves of enemies at the end and the phantom will come, signifying the end of the level.

Quarantine Zone

Take the ghost through the entire level. There are some shortcuts that are taken that can be seen in this video: http://www.youtube.com/watch?v=HXa0MGnsN4g
Once you get to the gondola ride. You can jump above the map and just wait for the ride to end. To jump above the gondola, go to the back of it. Jump on the ledge and then jump up the sloped surface. Walk all the way forward until you fall about 10 feet. You can now wait here and you will not be shot until the end of the ride. While going to this spot, do not jump or you will lose collision with your feet. At the end of the gondola ride, you can jump to the right and get on the other gondola to get to the end quicker. Be careful though, because if you die, you will probably have to redo the entire gondola ride.

Gravemind

Kill the enemies at the start. After the brute starts to talk, go to the side of the middle door to the left (if you are looking the direction that you spawn facing) Going to the inside corner causes the door to open. Stand at the precise spot that I do in this picture: http://i.imgur.com/X4ZwPMc.png Use the lights that I have circled to line up for the spot. You want to have slightly more light showing on the right side that the left. This will skip the waves of enemies that you have to fight. After killing the brutes and grunts that will spawn next, a carbine brute will spawn above the room to one of the sides. Kill him and then quickly make your way to the other end of the room. Run through the next few rooms as intended. When you get to the outside area with the lift, you can drop to the side of the lift and land on the support pillar. This skips having to wait for the lift to be active. Kill the jackal sniper and take his gun. Run through the next rooms until you get to the room with the lift. Drop to the lowest level of the room and stand next to the lift. Wait a couple of seconds and then Cortana will activate the lift so that you can drop down. I tend to drop my beam rifle for a brute shot in this room because it makes killing the enemies easier. Kill all the enemies in these rooms as quick as possible. After freeing the 2 sets of marines and killing all the enemies, make your way to the top level. Cortana will then say "Hostile reinforcements, coming down the lift" After she says this, drop to the second level and crouch between the lifts for approximately 5 seconds. This go back up to the top level. This will kill all of the enemies that are coming down the lift instantly. Then you can go up the lift faster. Pick up the beam rifle if you dropped it before going back up the lift. Once at the top of the lift grab the sword and sword cancel off of the elites that will be coming though the door. Sometimes you can sword cancel too fast and deload the enemies. This isnt that big of a deal, but it does make it so that you cant sword cancel for a few seconds. After making you way though the next few rooms you should be outside. Sword fly off the jack sniper that is across the way. If you have trouble sword flying, go to the right or left and you can jump above the map or you can just make your way across the gap as intended. Jumping above the rafters in the next part is faster, but then drop back down to ride the lifts. Continue through the level normally, but pick up the fuel rod gun that is next to one of the camouflaged elites. This will help in clearing the final room. After getting the fuel rod gun and making it through the next room, there will be a jackal sniper to your right. Kill him. This will make an elite get on the turret. Jump and sword fly off of the turret. If you are high enough you can prevent the hunters from spawning at the next door. In the final battle room kill all the enemies as quickly as possible, but kill them in this order: Elites, Hunters, Brutes+ bugs. This will stop a second wave of brutes from spawning.

Uprising

Grab the sword and either run through the level quickly or swordfly though the level. Once you make it outside to the "Step aside..." chapter, go above the map next to the tree. You can either jump off of the tree or use the fuel rod gun to get above the map. Once above the map, go slightly to the right until you are above the area where the level normally ends. Crouch on the large black spot on the ground and walk up the mountain side to end the level.

High Charity

Plasma pistol the elite with the sword and then finish him off with the carbine. The sword is used for swordflying. Once you get to the large chandelier room, you can either sword fly to the brute or ride the lift to the next section. Then step into the purple circle to activate the next lift. Ride that lift to the next area. Run through the next few rooms until you get to the elevator. It is possible to use the elevator to pressure launch to the top, but it is rather inconsistent. First start the elevator, wait a couple seconds, and then step off of it. Then crouch and make it so that your front foot is floating off of the ledge. This will cause the elevator to squish you and launch you to the top. However, if you do make it to the top and none of the enemies spawn, you will not be able to complete the level, so revert to last checkpoint. If you miss the launch a couple times, just ride the elevator. Once you reach the top of the elevator, kill a couple brutes and grunts and then stand next to the door across the room. It will change colors and then open if you killed enough enemies. Ride the next lift to the final room and quickly make your way to the other end of the room where the jackal snipers are. You want to be at the very far end to trigger the end of the level.

Great Journey

Steal the elites spectre at the start and then use the spectre to steal a ghost. Take the ghost to the wraiths and use the board glitch to kill the wraiths quickly. You may need to stop the brutes from stealing your ghost. Take the ghost into the building and traverse the hallways with it. Once you get to the point where you can ramp the ghost over the gap, line up, boost and hold A. The jump isnt that hard, but it is really easy for the brutes to knock you back and kill you. Keep making your way though the level until you get to the room with the jailed allies. Kill exactly 3 brutes and the door to the next area will open. there is no need to free any allies or kill more brutes. Kill all the brutes in front of the scarab to trigger the cutscene. Immediately after triggering the cutscene turn around and run backwards until the load zone. Then run back to the scarab. On your way back, grab a sniper from the ammo box. This will be used to kill Tartarus. You should hear Johnson say "Hah, how do you like it?" This will deload the wraith drivers causing the scarab to move more quickly. Then fly the banshee to the final building and just wait for the scarab to catch up. Flying the banshee into the corner that you see in this picture will cause the final battle room to load. It will only load after the banshee has blown up the door though. http://i.imgur.com/R1olwCA.png
Now that you are in the final room, either pick up a shotgun or a brute plasma rifle. Then wait a couple seconds because Tartarus is invincible. After the invincibility is up, shoot him with the sniper to drop his shields and then shoot him with the secondary. Repeat this process until he is dead. Be careful about getting too close to him because he can kill you in one hit. After he is dead the game is over, congrats.