Complete the single player mode game using any difficulty setting.
Lonely Medic
When you are playing xbox live and its 1 on 1 objective. I got something that will help you out. Start out as a luitenate on either team. Then throw down all the ammo you can. Then go to change class and choose medic. Then blow yourself up. And when you come back to life ammo thaty you threw down as a luitenate will be their and you are now a medic. So you have full ammo and medi-packs.
Air Strike in Multi Player
A lieutenant can call in an airstrike by pressing Zoom, then pulling the trigger on where you want the bombs to drop. There is a ten second delay.
Easy Head Shots
Turn off the automatic aim option to get a good head shot. Otherwise, you will lock on to the enemy's body.
Peek Around Corners
Click the left analog stick in and move the stick LEFT or RIGHT to peek around corners. You cannot shoot while doing this.