One of the most common complaints I hear about is a loss of flexibility and a resulting poor turn (photo). My favorite drill for this is what I call the hip blocker. When you fix the knees, it forces the upper body to turn much more correctly and slowly increases flexibility. As you swing, remember to turn the shoulders as far back as you can until the left shoulder is under your chin. In doing this, you'll feel a greater stretch along your left side. Finish by doing the same thing on the follow-through, but with the right shoulder under the chin. In time, you'll increase your ability to coil fully without using the hips. Remember, power is stored in the swing as a result of a big shoulder turn combined with a minimal hip turn.