There's a reason that there are no grooves on the putter. A putter isn't meant to launch a golf ball through the air spinning in one direction or another. When a ball hit with a putter its typically, though not always, on a putting green. Usually the golfer wants a smooth role of the ball and ideally it never even leaves the ground. As with many things in golf there is a tool for that. In this case a putter! A putter is designed to do one job really well - putt! And that means that a putter is designed to hit the ball in one direction and straight. You cannot put spin on a ball when putting (and you shouldn't try). There's simply no point in trying to make the ball turn on the green as a result of the way that you contact the ball will the putter by varying your stroke. It's the green itself that may cause the ball to turn right or left away from the hole and not in the straight line intended.
With this key knowledge, after carefully reading the topography of the green (i.e. deciding which way the ball is going to go after you strike it with the putter and send it on its way) you must align yourself with the intended target. note that the target is NOT necessarily the hole itself. Your target is the spot on the green that you're aiming which if you hit the putt correctly the undulations on the surface of the green (the hills and valleys) will turn pus the ball towards the hole. Once in position and you're aiming at your target the putt is quite simply You're only job now is to concentrate on bringing the putter straight back and straight through the ball toward your target.
Too many people line up a putt worrying about the break in the green and it's upcoming effect on the path of the ball. As a result, they tend to push or pull the ball to compensate for the undulations in the green. Trust yourself to have read the green correctly (if you're not great at it now you'll get better - its a skill in itself) and just putt the ball straight at the target you've selected. You may be surprised how often you're correct.
Because the putter (the club - not the person) will only hit the ball in one direction (straight forward), following the steps above will ensure that you hit the ball toward your target every time.
Once you get used to this stroke and practice a little you should save between 2-6 strokes a round depending on your handicap. Leave your comments below and let us know how much you improved.