Here's what I see amateurs do on breaking putts: They might read the right amount of break, but when they get over the ball, they look at the hole. When you do that, your aim drifts that way. You should look at the apex, or high point, of the break -- that's where you want to roll the ball.
Think of every putt as a straight putt to that apex. Here I have a 20-footer with about three feet of break, so I'll start the ball three feet out. The apex is my focus. If I get it there, the slope will do the rest. I like to imagine a six-inch strip in front of the ball that points to the apex. Start it on that strip, and I know I'm on a good line.
One more thing: The center of the hole shifts based on break. Imagine the hole as a clock face: The center is 6 o'clock on a straight putt, but it's more like 4 o'clock on this putt (below). Finding the new center will help you see the break and pick your apex.
The direction of your takeaway really dictates everything you do in the swing. You want the clubhead to start back first, followed by the hands and arms and the left shoulder. A good image is the triangle formed by your arms and shoulders. You want to move that triangle back in one piece. Another good feel is that the inside of your left biceps stays against your chest as you start back. The big mistake I see is swinging the club quickly to the inside, which often leads to weak shots and slices. Start back straighter with a one-piece move.
Butch Harmon, a Golf Digest Teaching Professional, runs the Butch Harmon School of Golf, at Rio Secco Golf Club, in Henderson, Nev.