Shanking the ball occurs when the golfer presents the hosel of the club to the ball at impact. This horror shot can be caused by the weight shifting forwards excessively in the downswing or by a swing path that is excessively in-to-out or out-to in.
Whatever the cause of your shanks, this simple drill from TG Elite Teaching Pro Gareth Johnston should fix this fault for good. By simply placing a tee peg inside the ball and trying to strike this instead of the ball, you should present the sweetspot of the club to the ball, not the hosel. Good luck!