One of the keys to accurate pitching is getting the clubhead moving consistently down the target line. A great way to practice this is to take a 10-foot piece of string and stretch it out directly on the target line of a pitch shot. Anchor each end firmly in the ground with a tee, and place a ball just on the inside of the string. Concentrate on keeping the clubhead (the end of the shaft) aiming at the target line or parallel to it throughout the backswing and downswing. Through impact, it's critical to keep the end of the shaft moving down the line with your thumbs pointing at the target line all the way.
A 10-foot piece of string is all you need to get your pitching on-target. try to keep your thumbs on the target line.