I remember reading about that in one of my PC Gamer issues, it looks pretty good.
It's like per class, you have like a certain "thing" to do. If you are a medic, you have to stick close to your buddies and heal or if you are a soldier, you have to run in and bash or something. I forget.. I'll just have to show you the imaged I ripped out of the .PDF file that came with the issue after it.