Level select cheat
Hold L + R and press Up(2), Down(2), Left(2), Right(2), B, Right, B, Right, B at the chapter selection screen
Kill types
Head shots are instant kills. Body shots require two or more shots for a kill.
Determining if enemies are still alive
Even if you shoot the enemy, he may still be alive. Make sure to aim your crosshairs at him and see if it turns red. If it does, it indicates that the enemy is still alive, and you must shoot him down more. Do not give the enemy the chance to shoot you from behind while he regains consciousness.