Concentration and repetition are keys to good putting. Look for uphill or downhill slopes. Read your putt from beginning, middle to end. If your putt has a lot of break in it, focus on putting your ball to a spot on the green, where it will then break to the hole. Trust your read, then focus on your speed.
Speed determines line.
A ball rolling at a fast rate of speed has less break than a ball rolling at a slower rate. Once you stroke the ball, watch it the whole way. If your putt rolls past the hole, pay attention to how it breaks going by the hole. Your line will be the opposite coming back. Develop good speed control and you will stop leaving putts well short or well past the hole.