Here are a few great coil drill tips sent to us from G.G. Blake that can be done at home to help you understand how it should feel to properly pivot during your back swing to produce an efficient coil.
My posture is so upright that I tend to rotate my shoulders horizontally. I seem to have trouble getting my left shoulder over my right leg which hinders my weight transfer and robs me of potential power.
First is a coil drill video by Tom Ward entitled "How to Coil for Power in your Golf Swing" that has helped me.
Second is another video from a professional golf instructor at Expert Village who explains proper "body and shoulder turn is a great way to coil your golf swing and improve distance" ...take a look.
Third is Jim Mclean with an interesting drill that helps with keeping the hips from traveling too much while uncoiling and minimizes the reverse pivot.