Plp with the rifles, I always have to remind them that don't have to crouch in order to get that pinpoint shot. Just standing there is just as good as crouching. Some people don't realize that and end up not being able to help when the team is on level ground.

Personally I really don't understand why people have to run all the damn time. I always go in bursts. Since I've played the game so many times I usually just run until I get to a point where I can expect a small group to be ahead. Then I crouch and approach.

The same with a horde. Once you stop hearing the drums I usually just crouch walk with the group when behind until the rest ahead of me have cleaned the room. If I'm point I always crouch and once I hear the drums stop I burst forward so as to not leave people waiting behind me wanting to go ahead. Almost always once the drums stop you can expect less than 7 more straggling infected coming your way before getting to a cool down spot where there is none of the normal infected around.

To sum it up. The best way to avoid FF is to let your gun do the work. Stay where you are and shoot. There is no reason to move around at all save to keep moving forward. PLP with the shotgun, LET the infected COME to you. PLP with rifles, snipe away but be warned that when there is a lull immediately start moving.
When there are infected crouch and move, when its clean go ahead and run until you see some infected and then stop, crouch, do your thing.