Choose a straight putt of about three feet. Set up a supported string using knitting needles, sharpened pencils, and string or twine. Push one knitting needle or sharpened pencil into the ground directly behind the center of the hole. Make 20-25 putts while making sure your eyes, the line on your putter, and the center of the ball all line up directly underneath the string or twine. This is a great drill for aiming because it allows you to see your initial alignment, the path of the putter head at impact, and the the face position of the putter at address and impact.