Stop pulling your puts

Whenever my putting goes off I know I slip back to my old bad habit of pulling the putter head to the left as I stroke through the ball. This is caused by moving my head too early and my shoulders then open up resulting in both pulling and pushing the ball. To fix this I place my ball on a 20cent piece 3 feet from the hole and once I set up to the ball I push the putter through to the hole. The trick with this drill is not to have a backswing and to make sure your eyes stay watching the coin until the ball goes into the hole. This will give you the feeling of keeping the putter head square and down the line on the follow through and by keeping your head down your shoulders will square through impact resulting in all of your putts starting on line.