1. Practice two-foot putts. Practice hitting two-foot putts so they roll into the hole dead center. Yes, you’ll get good at two-foot putts, but you’ll get good at six-foot putts and eight-foot putts, too.
A short putt that tumbles in from the side will miss from a longer distance, but a stroke that sends short ones in dead center will send the ball in from longer distances as well. That’s the point of this kind of practice.
I suggest two feet because that is a distance you should be successful at EVERY TIME. If it isn’t, move closer until you get it right every time, and then you can move back just a bit.
2. You’ve heard that it is a good idea to find a spot on the green on the starting line a few inches in front of your ball, and to roll the ball over that spot.
But the putter, which creates the rolling, needs to be travelling along this line, too. That means the imaginary line you visualize in front of the ball needs extend behind the ball, too.