There are many different variations of how to grip the putter just like in the golf swing. However, the main issue is to find a grip that fits natural to your feel. In the picture below, this is demonstrating the reverse overlap grip which is a common grip used by golfers alike. I use this and it helps me feel connected between both my hands so that I simply use my shoulders just like I mentioned in my previous posts on what I covered on putting. The grip should not be dictated by how powerful you stroke the ball, because power is not the issue in putting, it is feel.