Get in your set up position. Put a club across your chest. Rotate your upper body as far as you can with out moving your lower body. Do this on the backswing and on the follow through side. This is a great way to loosen up and it tells you how much you can separate upper from lower body. Then with the same club on your chest. Keep your upper body stable and rotate your lower body with out moving your upper body. Do this on the backswing and on the follow through side. Most players can not separate this action. So when you swing you should not be trying to restrict your lower body. It will cause to much tension and pressure in your lower back.
Learning how to blend the body and the arm and club motions. You start with posture and set up. You then go to impact. Once you identify impact you hit small shots from your impact position. You then make small swings where you feel how forces move in your feet and how pushing away from the force...