When You're in the level where you have to kill every "thing" coming through the windows, get the door to the radio open.Now you can go into every room and close every door(that has a switch).Go to the room with all the ammo and your Squad out(so they won't get in the way of your shots). next kill the "Things" coming in through the window and make sure there is no more. now go into the other rooms and do the same strategy.(when you run out of ammo, go to the room with all the ammo replenish your ammo.
Enable your Flare as normal, but do not throw it. Instead, wait until it gets low, then highlight another object using the D-pad. Now return to the Flare, and it will be restored w/o being used up.
Reloading your weapon when there are still bullets in the clip will cause you to lose those left-over bullets permanently. To conserve ammo, never reload your weapon until you've depleted a clip entirely.
When someone's trust is in the orange and they will not do anything for you, enter first person mode and aim the gun at their head for three seconds. They will now do things for you without good trust.
Don't waste blood test kits on team members since they get infected randomly and mutate within seconds of being infected; instead, use the test kits to prove that you are not, "The Thing" to keep your buddies loyal to you.
With Medics, always keep them alive if possible since first aid kits are few and far between, especially on the later levels. If you want a medic to heal a team mate, order the wounded team mate to stay put, then push the medic towards the patient.
Wait about one minute at the main menu to view a longer, uncut television trailer for the game.
More of a tip than a cheat. To avoid wasting ammo, and possibly getting killed/losing heath always close doors behind you when you have the option.
For example, on the level where you have to kill all the walkers, a walker will enter from the front door if you do not shut it.