Make a few strokes with the heavy (1.5 lbs) Gravity Grip, and you will instantly know where your hands should be in your stroke.  Your putter will swing naturally, and gravity will swing it consistently.

Bonus: The Gravity Grip actually gets its weight from the three Balls of Steel inside its tube. So, when you're not using it to perfect your set up, you can train with the Ball of Steel to improve your stroke.