When putting, the greatest influence on the direction of the ball is putter face alignment. It has an 83% effect on the direction of the ball. A great drill for helping with this is to put 2 tees in the ground approximately 1 foot in front of your ball along the target line. Set the tees 2 inches a part. Practice putting the ball between the 2 tees on its way to the hole. What you will notice is if the toe of the putter face closes at impact your ball will strike the inside tee. If the toe of the putter face opens at impact, the ball will strike the outside tee. If you keep the putter face square to the target, the ball will roll between the 2 tees and in to the hole. Begin the drill 2 feet from the hole and work yourself out to 25 feet.