Instructions
Push the left control stick lightly forward to walk at a slower speed than usual. The amount of pressure you put on the control stick controls your speed; pushing the control stick all the way in the direction you want to go will make you run. Sneak up behind an enemy soldier.
Press "L1" to point your gun at the back of a guard. You will automatically tell the guard to freeze, and the guard will put his hands up and drop his weapon. Press "R1" while you're still out of arm's reach of the enemy soldier to shoot him in the back.
Walk up to the enemy soldier and press "R1" when you can touch him to put him in a choke hold. Tap "R1" repeatedly while the soldier is in this choke hold to snap his neck.