John, the putting grip like the actual putter itself is highly individualistic. If you enter into the realm of long shafted putters it's different still.

What I would advise you to do is avoid forming a grip that is too long, especially when you're learning. By long I mean the distance between the top hand and the lower hand - Bernard Langer uses the reverse overlap - the left below the right. Many people adopt this when putting trouble sets in but really you should concentrate on getting the basics before you start tinkering.

Lots of people use the extended left index finger (if you're right handed.) The finger extends straight to the ground resting on the four fingers of the right hand. It is thought this stops the left wristing from flicking at the ball (club head passing the line of your hands before hittng the ball) something you must avoid. I use this grip but have adapted it for comfort. My left index finger curls into the grip and fits between the index finger and second finger of the right hand. This feels very solid and comfortable to me and I think that's important.

Whatever you adopt make sure it's comfortable for you and practice. If things don't go well it could be your grip but also consider the rest of the putting stance and action.

Check out this link for some putting tips.

http://www.ritson-sole.com/golftips/archive.htm

Paul