For multiplayer coop mode, formations can be very helpful. In formation A, player one stays a little while back with a pistol or sniper and protects player two, while player two moves in with another weapon of choice (preferably human or covenant rifle). Then, player two pulls out a pistol or sniper and hides behind something while protecting player one, who then pulls out his/her weapon of choice and moves toward the enemy lines a little (of course, whoever has out their weapon of choice is also shooting the enemy). Cotinue this process for as long as need be for the time. This process can also be used for more then two players.