The problem: Taking the club back outside the target line and swinging outside-in on the downswing.

Simple fix: Golf shops sell what is basically a foam roller suspended in the air to help guide your swing, but Goldstein says an empty range basket does the job even better. "Place the basket a half-inch outside the ball and two inches behind it," he says. "If you can avoid the basket on the takeaway and on the downswing, that's the path you want."