First of all, get a wired controller. reasons: it wont die on you and you have a better response time.
Second, get a small HD tv. reasons: threes no video lag and you don't need to turn your head to look to your left or right
Third, get a good online connection so there's no lag
Fourth, Try to buy a Turtle Beach headset. It makes you able to hear surroundings more clearly and you can switch between game chat or just your audio or both!
also, you can also use these for Call of Duty!
edit: VIDEO LAG IS IMPORTANT! REASON: IF YOU TURN A CORNER AN ENEMY CAN SHOOT AT YOU BEFORE YOU SEE HIM/HER!
reply to Adam: its 4 shots