The three simple keys to consistently sinking short putts are: making contact with the center of the putterface, making contact with a square putterface that's on-line to the target and accelerating the clubhead through impact. If you learn to do these three things, your short putting, and overall putting, will improve quickly and should stay solid for good.
To ensure that you learn to make center contact, begin by placing two tees on the sides of your putterhead (one on the toe, one on the heel). Practice stroking putts without making contact with either of the tees, and continue until you find you can strike the ball cleanly every time. Work on this drill regularly, and you'll soon find the center of the clubface regularly.
Once you feel comfortable with the first part of the drill, place a shaft on the ground next to the tee that's outside the toe of the putter, and make sure it's parallel to the target line. Practice stroking putts, being certain to avoid contact with either one of the tees, while also keeping the putterhead perpendicular to the shaft on the ground through the impact zone. Keep working until you can do both things at once, and you'll have the clubface square at impact while also making center contact with the ball.
The final element to conquer is finding a way to keep the putterhead accelerating through impact, which is critical to imparting a tight, end-over-end roll on the ball. Most golfers make the mistake of taking the club too far back, which leads to a decelerating clubhead through impact. To prevent this problem, take a third tee and place it behind the ball (at address), relatively even with your right toe. This tee will serve as a barrier and prevent you from taking the putter too far into the backswing, forcing you to accelerate the putterhead as it swings into the ball. Practice stroking putts combining all three elements of the drill (swing between the tees, along the target line and not too far back in the backswing), and soon enough, you'll feel confident on the short ones, which, in turn, will give you more freedom and confidence
to go for those 12- and 15-footers for birdie.
Kevin Scheller works with PGA and LPGA professionals, as well as recreational golfers.