If your problem is pinpoint accuracy, then it's likely you hit a lot of greens, just well to one side or the other of your ultimate target, the hole. That means you're probably left with many a lengthy putt, the kind you're glad just to roll up close, tap in, and walk away with par. So if you can't successfully lag long putts close, you're in for a lot of frustration, as well as wasted strokes.

Don't Stress Out
The prospect of three-putting usually causes a player to tense up mentally and physically. The hands, wrists, and forearms get tight as you try to control the putterhead; it's similar to trying to steer the clubhead when faced with a full shot to a tight landing area. Both "steering" and "controlling" lead to poor results. On the green, you produce a poor swing path and a jerky or decelerating stroke.
You must learn to relax and let the putterhead go. Take a deep breath, let it out, then release so it swings freely. Concentrate on feeling the weight of the clubhead. Let it coast to a stop on the backswing, then swing it forward at the same speed you swung it back on. Don't control the putter, let it swing. You'll find that your instincts have a better sense for distance and direction than you do.

Magnifying Your Mistakes
Because you're making a bigger stroke on a long putt, mistakes will be compounded: Mis-hit a 10-footer and it comes up two feet short; but mis-hit a 50-footer and it stops 10 feet short. So it's imperative that you keep your body and head still to ensure that the clubface returns to the ball solidly.

Find an Intermediate Target for Speed and Aim
The hardest thing about rolling the ball close is getting the distance right. Most people gauge a putt's distance by how hard they have to hit it. Instead, pick an intermediate target -- a spot on the green on your intended line about 10 feet in front of the ball -- and calculate what speed the ball should be rolling when it reaches that spot so it will lose momentum near the cup. Imagine what would be too fast, too slow, and just right. Stroke the ball toward the spot at the speed you've determined.