Depends on the game, and how I'm feeling.
In Team Fortress 2, I'm usually the Medic healing on the front lines. If I'm a Soldier or a similar class, I usually charge if I have some teammates with me.
In games like MW2, I usually play a conservative style, a mix between stealth and assault, you can say. I run a silenced weapon and use perks like Cold Blooded to stay off the map, and Scavenger to help long-term survival.