The Proper Putting Grip:
Start by holding your putter as you would any other club – primarily in the fingers of your hands. Raise the head of the putter to about chest height and notice how there’s an angle between the club shaft and your forearms.
Loosen your left hand grip (for right-handed golfer) and use your right hand to tilt the club head down until the shaft of the putter is parallel with your left forearm. You should feel the putter grip pivot over your palm until it rests under the pad of your left thumb.
The grip should now run across your palm, in line with the lifeline.
Close the fingers of your left hand on the grip and notice that your pinkie barely touches the grip.
Now place your right thumb against your left thumb and slide it down the grip one knuckle, until your thumbs fit together like jisaw puzzle pieces.
Close the fingers of your right hand ensuring that the grip also runs across the palm of your right hand, in line with the lifeline. Experiment with different ways of placing and overlapping your fingers to find what is most comfortable for you.
Most importantly, take your address position and look in a mirror to make sure that your forearms are now in-line with the putter shaft.