Get into 3rd person cage match with ur friend. have cold blooded, scavenger, a stinger, tac insersion, and whatever gun ur gonna use for headshots on ur class. For your killstreaks have care package, sentry gun and emergency air drop. Both get an 8 killsteak to get all of them. Just keep doin the care package glitch, call em in and have ur friend take them out with the stinger or knife the sentry gun and u do the same. If u can do the care package glitch fast enough u could get up to 30,000 xp (at least 10,000-20,000). My friend told me the care package glitch does not work on PS3 anymore but i know this works on the 360. GT:X2XTX2X