While aiming, relax and let your pin float. Hold the bow as still as possible while remaining relaxed, but don't try to force the bow to remain rock-steady. Trying to eliminate all motion will cause a lot of unnecessary tension. Remember, you can't hold the bow perfectly still -- nobody can -- so just let it float naturally.
The worst thing you can do while aiming is to time the shot by punching the trigger when the pin crosses the spot. Punching the trigger will create all sorts of problems down the road. Just relax and squeeze off a surprise release as the sight continues to float.
Some people focus on the target while aiming; others focus on the sight pin. Better, in my opinion, is to focus somewhere between so both the target and sight pin remain in semi-focus.
It's best to keep both of your eyes open while you're aiming; however, some people have a nondominant eye that tends to take over during the aiming process. If you experience this problem, you need to close your nondominant eye. Some archers compromise by squinting the nondominant eye, which gives a fuller field of view but prevents the wrong eye from taking over the aiming process. Whatever method you choose, remember that consistency is the key to accuracy, so do it the same way every shot.