I've learned that you need to anticipate where people are going...be more on the defensive side. Run to a place, hide in an area and look for some enemies...once you kill a few move to a new place. Always stay on the perimeters...RARELY go into the heart of the map since there you will be open from all angles. If you run and gun stop. Take conservative shots. If you are firing on an enemy and he runs, don't always run after him for the kill because often there is someone right behind using him as bait...I do that all the time. I let a teammate go sometimes ahead and I follow behind and protect his back and pick up 1 or two kills.

Also the BEST killstreak combo is predator missile, harrier, chopper gunner. Get 5 kills and you are almost guaranteed chopper gunner. Use the Predator missile to clear a safe passage to hide while you call in the harriers and let them get the 4 kills for the chopper gunner. If it gets shot down and you are 1-2 kills from CG hold back and play REALLY conservative. Once you get the CG it doesn't matter where you lay prone to do the killing as long as you are semi hidden since if anything you can work towards another CG your next set of lives.

I really suggest SCAR with extended mags. Scavenger, stopping power, ninja. stun and semtex.