Here here, good post!, situational awareness is a big one, especially with tank crews not paying attention out their window 
Wolves.
Wolves.
I would also like to add this:
Give yourself options!
I was playing snowyforest last night, and the germans only blew up one piece of barbed wire the whole round. I had my DP and blasted all who came near. It was a death trap for them. You can't win by doing the same thing every time, it just gets your enemy more and more aware of your moves.
Speaking as a member of the "get out there and get it done" crowd, I have to admit that I often shoot at the feet of spawn snipers. Never TKed one yet; a good burst from an MP40, accompanied by some succinct chat usually gets the job done.
I will say that it is way to hard to suppress with an MG. Too often I'm sniped by the rifleman I'm pouring fire on. That's something that needs to be fixed before proper suppression can be achieved.
When sniping, remember that keeping people out of the capzone is your biggest priority. DO NOT SNIPE FROM OUTSIDE THE CAPZONE!
Get in the capzone, find a safe spot, and shut down the enemy reinforcements - like you are supposed to.