Early in my career, I had the chance to play several rounds with Jack Nicklaus. On these occasions I studied his putting intently, because he was killing me on the greens. One thing that consistently caught my eye was how he held his finish and watched his putts roll out. It didn't take me long to realize something: Good putters learn from both their makes and their misses. You can watch Tiger Woods and Phil Mickelson on today's Tour do the same thing: they store information in their memory banks about how their putts roll versus how well and in what direction they stroke them.
The main benefit from holding your finish comes from internalizing the feel of the stroke you just made, and then correlating that feel with its result, good or bad. This system works because the feel of your stroke is still strong in your system. Once you stand up or move your feet, the feelings of your stroke disappear.
Holding your finish will also help keep your body still and improve the consistency of your stroke. I'm sure you've been told to not move your head until you hear the putt drop, but I don't like that advice. Instead, rotate your head while keeping the rest of your body still, so you can watch the ball roll and get a feel for your stroke. You'll learn how solid your stroke was, if your ball speed was good or bad, and whether your line allowed for the proper amount of break.
Holding your finish is such a good idea, I can't believe more golfers don't do it. I'm sure it will improve your putting over the coming years.
Read more: http://www.golf.com/golf/instruction/article/0,28136,1892429,00.html#ixzz0m2DyIRKd