distance control is the most important part of putting to eliminate three putts. What helps me with distance control is two simple keys
1) I use my feet as a measurement tool for distance that I take my putter back too to help judge distance control
2) I always follow through with the same distance on each putt, keeping the same tempo. The only time I will not do this is will very short putts within 3 feet.
I found that this is the easiest way for me to judge...