Many golfers read a putt from behind the ball then take a few practice strokes and putt. The problem with this is your eyes can play tricks on you.
A great way to get the feel for the speed of a putt is to read it from the side by looking at the ball then following the path to the hole with your eyes. In order to get an even greater feel for the speed of a putt is to do this by pointing your putter head at the ball then trace the path to the hole with your putter head while maintaining the pace of the putt. This will help develop the speed of the putt.