If the upper body is not stacked up over the lower body at address, at the top of the back swing the upper body will lean forward towards the target. This position at the top will create a steep downswing from the outside with a ball flight that will pull to the left, or a weak slice to the right of the target.

To fix this problem get out a club, face a mirror and set up at address. The upper body is stacked up over the lower body if the left shoulder and left hip match. "Note" the right shoulder should be outside the right hip. If the left shoulder and hip don't match, raise the left hip and the spine will tilt back a bit.

From this position at address the upper body can make the proper rotation to the right side in the back swing.

Neil Wilkins, Director of Instruction at Sienna Plantation Golf Club