Instructions
Use precision weapons, such as sniper and assault rifles. One- and three-shot burst precision weapons are made for marksmen. Get used to these weapon first, and then practice using sniper rifles.
Pace your shots. The more methodical you are in your shooting, the more your shots will hit their target. The faster you shoot, the more your reticule increases and loses accuracy.
Crouch while shooting. Crouching gives you the most stable position for shooting, thus increasing your accuracy. Running and gunning will decrease your accuracy tremendously.
Learn the height of the opponent. This can only come from repetition. Play the game online as much as possible and it will become second nature to always place your weapon's reticule right on target.
Keep an eye on the radar for incoming enemies. The more you know about your enemies position, the more ready you will be to shoot first and accurately.
Avoid sprinting when enemies are close by. Sprinting increases the time it takes to bring your weapon into position for a shot.