The new PGA champion, 25-year-old Martin Kaymer from Germany, has a great swing -- a modern move where his legs and hips move very little while his upper body coils by turning against a resting lower body. It's a young man's swing because you must be flexible with no injuries, but it's a very effective way to play.
To create coil during your backswing, the left arm (for right-handers) swings up across the chest, then during the downswing, it stays melded to your chest so the full force of your body is behind the club at impact. To start the swing, your weight shifts into your trail hip without turning your hips much. The key is not to move off the ball. The feel is that your legs are in cement. Of course there will be some rotation of your hips, but only as a response to the pull of your shoulder and arm action.
Per the drill below, neither your shoulders nor your chest should turn until they are pulled around by the front arm as it swings away from the ball, the sequence being arm, then shoulder, then chest. This way there is no slack in the backswing, which is a good thing because slack breeds slap, i.e., looseness in the backswing causes a weak, slapping action through impact.
By swinging the left arm to create maximum stretch, you keep constant tension on the muscles, which leads to a powerful release of this tension at impact. Also, the more stretch you create, the wider your swing arc will be, which means more clubhead speed and power.