Whenever I go to the putting green,I always use two knitting needles and string. What you do, is tie the string to the needles and place one behind the hole and one behind where you are putting, so that the sting is lined up over the ball. Then you putt trusting the string. (you might have to adjust the string for alignment). But this drill really helps with trusting the roll, getting to know the speed, consistency with putts, and it helps me stand over the ball. This is a drill Luke Donald, no. 1 player, and Aaron Baddely, best putter on tour uses.