Do you have a problem striking the ball solidly on a consistent basis? Do you tend to hit behind the ball? Do you struggle getting the ball to go into the air? Do you lack power? If so, it could be that you have too much lateral body movement through impact.
This isn't to say lateral movement isn't allowed. In fact, the left hip should shift laterally forward until it's directly over the left heel. The key is to shift laterally, not by flexing your left knee, but by transferring your weight to a straight left leg. This is called posting-up.
Posting-up simply means straightening your left leg as you drive your weight into the finish position. You can check this by either videotaping your swing or having your playing partner watch your lower body through impact. As you drive into the ball, your left knee (for a right-handed golfer) should be straight and devoid of flex. This creates a lower-body motion that can be easily repeated and that provides a consistent impact position.
At impact, PGA tour players achieve a position that situates their left hip higher than their right. Put another way, their left leg is longer than the right leg. At GolfTEC, we define this as hip tilt. The PGA tour players' average hip tilt at impact is 14 degrees to the right. Amateurs typically don't post-up well and generally have around three degrees of right hip tilt at impact.
Use your lower body efficiently by posting-up. When you do, you'll hit the ball farther and with greater accuracy.
PGA teaching professional Scott Young is the Director of Instruction at the GolfTEC learning center in Dallas, Texas.