I find practice putting to be much more basic than people think it is. In college, I was taught to practice extremely long putts and very short putts. The PGA Tour average from 3 feet is nearly 100%, about 70% from 6 feet, and close or under 50% from 10 feet! Assuming that the average player is not as good as a PGA Tour Pro, I would bet that the averages are more like 90% from 3 feet, 45% from 6 feet, and 20% from 10 feet. I ask my students why they would practice putts they can not make routinely?
Practicing putts from inside 3 feet will help you in many ways.
1. It will improve your stroke
2. Help your alignment
3. Build your confidence
The routine I would like to see players use would be to start with one or two balls and hit putts from very long distance. The goal of these putts is to simply learn the speed of the greens. After you have learned the speed of the greens, go to inside 3 feet and make anywhere from 25-100 putts. Learn to love watching the ball go into the hole and the solid feeling you get when you hit a perfect putt right in the center of the hole.
Remember: Practice really long putts to get the speed of the greens followed by very short putts to build confidence in your stroke.