Correct putting grip

After you have gripped the putter both thumbs should point straight down the shaft. During the backswing the putter face should not roll open. If you feel the thumbs roll to the right in the backswing that means the clubface is opening and the "Y" is not intact.

Use the "Y" to develop a consistent putting stroke by maintaining the "Y" in the backswing you can develop a stroke that will have the same amount of impact every time. The wrists have no place in the putting stroke. Using the "Y" you can develop a putting touch for all distances. It is very difficult to develop a putting stroke using your wrists. Any wrists movement in the putting stroke will add loft at impact and inconsistency to your distance control.