My Setup Key
I focus on two fundamentals when I address the ball:
1. My arms hang loose and perpendicular to the ground. You should never feel like your arms are jammed or that they have to reach for the ball. If you bend from your hips and keep your back fairly straight, you'll nail this and swing more freely.
2. I flex my knees so that my shoulders are in line with my hips and my knees are in line with the balls of my feet. (Practice this in front of a full-length mirror — I used to). When I get this right, I feel perfectly balanced.
One more thing to know: Take a narrower stance with your irons than you do with your woods. If your stance is too wide, you'll tend to tilt too much away from the target. That's okay with your driver, but not with your irons.