The quality of your sand shots will only be as good as the quality of your setup. In other words, if you don't address the ball in a way that stabilizes your lower body, you won't be able to execute. I'm constantly checking my bunker address fundamentals. Here's what I look for:
Grip: A weak hold [Vs formed by my thumbs and index fingers pointing at my chin] levels the shoulders at address and makes it easier to release the clubhead open.
Stance: Make it wide -- shoulder-width at the very least -- and flare out both feet. Flex your knees so that your weight is held in the front of both thighs. This should stabilize your lower body. Excessive hip turn is an absolute killer in the sand.
Club: Lower your hands to just above knee height, allowing the clubface to rotate open and expose the bounce.
Ball position: Make practice swings in a bunker and note where the club enters the sand relative to the position of your feet. Do this until you have a good idea of where your typical entry point occurs. The best ball position for you is about two inches ahead of your natural entry point.