Putting is probably the most individualistic thing we do.  One common element we see in great putters is their eye and head position.  Even though you see many different stance, grips, and body positions, one common position among these great putters is their head is directly over the ball, with their eyes also directly over the ball.  This allows your eyes to be directly over the path at which you intend to putt the ball on.  This will also encourage the swing path of the stroke to move back and forth along this intended target line.  Remember, place your eyes right above the ball and.  You can check this by dropping a club from between your eyes.  This will show you proper eye and head position.