Just as the eyes are the windows to the soul, the setup in putting is the window to the stroke.
If left alone, the stroke will mirror the positions established at address. Set up well, and your stroke will flow naturally; set up poorly, and you'll be fighting yourself the whole way.
It's easy to pick out good and bad putters by looking at their setups. But every golfer has the ability to putt as well as a tour pro because, physically, putting demands very little. You don't have to be strong or fit or flexible. But you do need to get into a good setup. Here are the steps I teach. —With Peter Morrice