
In case you don't know. The yellow arrow is you, the green is your teammates (sometimes blue when you're in a party), and the red is the enemy (only when advanced UAV is up).
So even though it seems like a good idea strategically, don't go prone in a doorway or hallway when it's the only way out of the room, and don't run behind some one who is. This way you won't possibly get them killed and they won't get you killed.
I know this should be common sense, but remember, many of those who do play these games lack it.