Ok. here it is. A very useful way to know if someone is coming after you is by scouting. Heres how you do it. On co-op or multiplayer, tell one of your squadmates to hold still. Using the Y button, jump on his head. If you are skilled enough, then you will be standing on his head. Use this method in blood gulch to scout around and get an early warning if someone is coming after you. Good luck!