How you grip the putter in the putting stroke is different from how you grip it in the full swing. In the full swing you grip it in the fingers and underneath the heel pad, and the reason you do that is so that you can lever the club in the backswing. In the putting stroke you want to grip the putter in the lifeline of your left hand and then match your right hand to your left hand for a right handed golfer. When you place the putter in the lifeline of the left hand it gets the back of the left hand and the putter face lining up together. A checkpoint to make sure you have it correct is if you grip down on the putter the grip is between both forearms of the arms. Now if it is incorrect, and the grip is too much under your heel pad, the shaft will be below your left arm and your right arm. So it is a great checkpoint that once you get it in the lifeline of the left hand grip down and see that the shaft and the forearm line up. From there what I would like you to do is get a golf ball and draw a line on the golf ball. When you putt it should roll end over end in the direction of the line (you should see a straight line through your ball as it rolls). This way you will know if the path is correct and the face angle is correct. Let’s go ahead and try one. I am going to place the ball down with the line drawn on it aimed at the target, and if I have the correct grip and I have the correct path and face angle, this will roll end over end. So give that a go to improve your putting.
Mike McGetrick heads the Mike McGetrick Golf Academy which is located in beautiful Denver, Colorado and features one of the most modern golf instruction facilities in the world. He is listed as one of Golf Magazine's Top 100 Teachers and Golf Digest's #7