Instructions
Load "Call of Duty: Black Ops" on your console, select "Multiplayer," choose "Join Match" and select a match type to begin playing.
Choose the weapon class with your sniper rifle in it when prompted and begin playing the game as you normally would.
Pull the left trigger on your controller when you see an enemy player. The aim sight on your sniper rifle will now drastically shrink in size, making it easier for you to focus in on the enemy.
Pull the right trigger on your controller once your sight is focused on the enemy to fire your sniper rifle. You have now succeeded at making the aim sight smaller on your sniper rifle. If you aimed with the left trigger quick enough, you also should have an enemy kill now.