Even the best address position can get derailed by a common backswing mistake sent to me on Twitter all the time.
When you set up, you establish a certain amount of forward bend from your hips, which creates an angle between your spine and lower body. If you want to hit the ground in the right spot and get the right amount of it—two keys to hitting solid shots—you need to retain the posture you set at address all the way through impact.
Instead of turning the shoulders around the original spine angle, many amateur golfers stand up out of their posture and turn their shoulders on a flat plane (below, left). That kind of level turn tends to move the arms too far to the inside and makes it difficult to get back down to the ball.
The more you can rotate around a consistent spine axis, turning your left shoulder under your right (below, right), the more consistent contact and ball speed you'll be able to produce.
*Hank Haney is based at the Hank Haney Golf Ranch, Lewisville, Texas. To get fixed in Golf Digest, send Hank your swing on Twitter: @HankDHaney.