A couple more tips.
Do not underestimate the value of suppressing fire. See a bunch of tracers coming at your teammates but can't see the actual guy shooting? Put some fire down on where it looks like its coming from. If you don't get him, you'll at least force him to put his head down.
Smoke grenades are best grenades, especially on Push. They are invaluable especially on that one map where the Americans start on the bottom of that hill and need to push up to the town.