Personally, l like a putting stroke that uses the arms and wrists; however, on a very long putt, you will need to use your shoulders and take a longer backswing and follow-through. Play the ball off the left heel and place your feet square to the line.
If you are taking the putter too much outside the line, your weight could be on your toes and your eyes might not be over the ball. There are two reliable ways to be sure your eyes are over the ball. Either hold the ball at eye level and then drop it and see where it lands, or else hold your putter shaft straight down from eye level to the ball.
A good putt dies out straight, a bad putt slithers away. Be decisive when you putt, decide what you want to do on a putt and then go ahead with confidence, even if it should prove to be wrong. You should try to carry your putter in your left hand, or in both hands but never carry it in your right hand alone. Think of your left hand and arm as an extension of the putter shaft.
Out of Bounds: Be careful when you place the putter behind the ball by only using your right hand. By bringing your left hand onto the putter later you run the risk of inadvertently changing the aim of the putter head.