Sometimes you just need to relax and wait. Shoot for the head. It's an obvious tactic, but only the best of the best shooters should practice this approach. It's much easier to get a body shot then get a head shot. But if you're that tuned, then make a habit to hit nothing but their heads.
Any good team needs diversity.
You can't have 3 guys that all love to Snipe, or 3 guys that all want to rush. Each teammate should have a specialty to compliment the rest of the team. Very map dependent. Most cases you just stick together. But again, it's very map dependent, as you will see when I go over maps individually.