When you have killed an enemy with your last round of ammunition, approach your victim and switch your weapon with him and then trade back to your original weapon. Doing this will give your weapon full ammunition.
If you want to display the coordinates of your current location at the lower right-hand corner of the screen press L1 + L2 + R1 + R2 during gameplay. It may take several attempts before this code takes effect.
Like the title says, this is more of a glitch than a cheat. This is for putting any helmet that you ALREADY have unlocked on any armor. It won't work with helmets that are still locked. First go to the Armory. Then change the armor of the class that you want the helmet on to the armor that has that helmet. Press the back button and save you're changes. Go back to the same class again. Change your armor back to what you want it to be, and select headgear that you do NOT have. Press back. Wa-la! You will still have the helmet from the other armor on! I know that this works, I've done it. If it doesn't work something went wrong along hte way, so just try again. This will work for all factions too.
Get a Medical Kit and heal and resuscitate your allies, this is an easy way to get Experience points. When you heal their health you will receive 5 Experience points, resuscitate them and you will get 10 Experience points. When you reach level 4 you can average 200-400 Experience points a fight.