Bad body alignment is a primary cause of misguided shots. Players sometimes don't realize their alignment is askew because in checking it, they pay attention to their feet and hips, which they can see, ignoring their shoulders. It's easy for the shoulders to turn open or closed while the feet and hips retain proper alignment. And it's nearly impossible to hit straight shots if the shoulders aren't square to the target line.

After settling into your address position, hold a club against your
shoulders and see where the shaft points. If it's aimed to the right of your
target, your shoulders are closed; if it points left, the shoulders are open; if
it seems to point directly at the target, the shoulders are square to the target
line. Repeat this test from time to time until you can sense your shoulders are
square.
Private Lessons 1999 Times Mirror Magazines, Inc., used under license by GolfServ Online, Inc. Instructional information provided by Golf Magazine.