The number one skill in putting is distance control. The ability to hit the ball the correct speed and distance helps you to eliminate 3-putts and make more mid-range putts. I think the second most important part of putting is the four foot putt.
According to Mark Broadie in Every Shot Counts, the most important putt distance for amateur golfers is four feet. This distance accounts for 13% of the total strokes lost against pro golfers. The range from three to seven feet accounts for 46% of the total strokes lost. Developing your skill in the three to seven foot range will help you to save strokes and reduce the number of 3-putts.
The main key to making more putts in the three to seven foot range is solid contact. Hitting the ball in the center of the face will encourage consistent speed and direction. Off-center hits will vary the speed and the starting line. To work on hitting the ball in the center of the face more often, you need feedback. Find the sweet spot on your putter face and then wrap two rubber bands around the face on either side of the sweet spot. You can also purchase a training aid from Eyeline Golf called the Sweet Spot 360. The Sweet Spot 360 is a piece of foam that sticks to the putter face and has an opening in the center allowing your ball to make contact with the sweet spot. Practice hitting putts feeling impact in the center of the face.
You have likely seen Phil Mickelson practicing his short putt drill with golf balls circling the hole. Take 6 to 12 golf balls and set them up around the hole three feet away. Your goal is to make all in a row without missing. Once you make all of the three footers, move out to four feet and try again. Another good drill is the Triangle Drill. Setup at three different holes on the practice green placing three balls at three feet around each hole in a triangle shape. The goal is to make all nine putts without missing. Make all nine and then try it again from four feet.
Master your distance control and make more four foot putts and you are on your way to playing better golf.