Do you use your tryhard gun? Do you run the high streaks? Do you use weapons that you need to level up?
I usually just run UAV, HKD, and CUAV anyway. I'll switch them if they talked trash. When I see a noob lobby, that's my time to try to level up random crap that I don't have much unlocked for. I could care less about my KD or crap like that so I won't run the high streaks or anything unless they talked trash the previous game.
I always check people's SPM when I enter a lobby, and when I find low SPM players with low K/Ds, I use it as an excuse to run medium streaks (as high as Warthog) and try to just screw around with knifing, litterbugging, or using akimbos. Usually, I end up having a lot of fun for two or three games before they all resort to camping. --- Soon to be hosting Critical Hit game and movie reviews via YouTube.
Lately, I take it as an opportunity to practise the canceling involved in swapping weapons on my Overkill shield classes. It's tough to master, so yet to get a gameplay that I'm happy with sharing with the world, but I'll get there eventually. --- http://www.youtube.com/mitchacho