Can anyone give me MW2 advice?

I'm a run and gun type player but i started "camping" more today.I got 2 chopper gunners out of about 5 games. But i have never gotten above a 7 killstreak until today. What guns should i use to get higher streaks and waht perks. Also what game typed are best? I was ffa when i got the chopper gunner. Im elvel 37 after prestiging once. I usually see someone and try shooting them but they knife me lol(i hate commando)Any advice on getting better, what guns to use, and how to be more patient would be appreciated.thanks:)