The putting stroke is made by the shoulders controlling the movement of the arms and hands.  The shoulders, arms and hands move back and through in unison, so that the angle in the right wrist remains constant throughout the stroke.  This movement ensures that the putter stays on the correct path, which is just inside the target line as the length of the putt increases and goes straight through towards the hole on the follow-though.

To practice a square clubface position, imagine the palm of the right hand is like the face of your putter. Find a tennis racquet and hold it in your right hand as if it were a putter.  Place your left hand on your shoulder to remind yourself  to rock the shoulders and make practice strokes. Concentrate on keeping the face of the racquet and your palm square to the hole throughout the stroke.  Notice how the angle in the right wrist almost increases in attempt to keep the clubface square.  Hit putts with your right hand only to help create clubface awareness.  When you place both hands on the putter, you will have a better sense of the path and clubface position.