Explore the Green

When you are on the practice putting green, putt from different positions around the hole and putt to different holes on the green. 

Avoid standing in one spot hitting putts over and over again, because eventually even with a bad stroke you will start getting the ball in the hole and this practice only teaches you how to sink that specific putt.

Instead, move around and explore the various putts you will ultimately be faced with on the course.