You're a fairly good putter inside 15 feet, but you struggle with your touch from long range, which leads to more three-putts than you're comfortable with. Those three-putts, after all, can mean the difference between a really solid round and shooting 3- or 4-over par! Here's a great drill that can help you groove the proper-length stroke from long distance and make those costly three-jacks a thing of the past.
Pace off a 50-foot putt on the practice green and lay your 5-iron down on the green parallel to the line you want the ball to start on. Set your ball down in the middle of the shaft and, using the 5-iron as a guide, swing the putterhead to one end of the club on the backstroke and the other end on the through-stroke — you want to be equidistant on both sides of the ball. Practice this until you can consistently leave your putts hole-high.
Why a 5-iron? The length of the 5-iron shaft represents the perfect stroke length for a putt of 50 feet, and this teaches you how to make solid contact, since that's the only way to consistently get the ball to the hole. If you find that your putts come up too short or too long, change the tempo of your stroke — i.e., make it faster or slower — but DO NOT change the length! If you can learn to control your distance from 50 feet, you'll not only stop three-putting, but those 25- and 30-foot putts will start to look a whole lot easier as well.