Putting is very individual in many aspects. There are many methods and styles of great putters -some set-up with  open feet, others stand closed. Some have bent arm positions at address, others keep their arms straight. Just look at the many different putters for sale on the market today, they accommodate the player for different preferences in putting styles.  However, all great putters, have six basic fundamentals in their putting stroke. These rules are what determine real long term success in putting.  

1. The front eye is directly over the ball.  (It is easier to aim when your eyes are  over the  line of the putt).
    
2. All the motion is with the shoulders and arms. The motion is like  a clock's pendulum, the arms move , but the head and hips remain absolutely still. The  wrists do not break. (This keeps the stroke simple and efficient with few moving parts.)
    
3. The shoulders are parallel to the target line, not open or closed.
    
4. The putter travels  back and through along the target line as long as possible without affecting the natural path of the stroke. (As the stroke gets longer,  the putter slowly begins to move inside the target line on the backswing, moves  to square, then returns inside the line again on the forward swing.  This is  merely to accommodate for the natural movement of the putter around the body as the stroke gets longer.)
    
5. The blade remains square throughout the stroke.
    
6. There is an Acceleration through the putt.  (Slow going back and accelerating  going through.) Most people find practice putting to be boring and not worth the time. Consider this, putting makes up 35% to 50% of all strokes taken in a round of golf. There is no doubt that shaving strokes in putting can lower your handicap significantly. Below is a siple drill that works on many of the fundamentals above.

Please See - String & Pencils Drill