The single best way to reduce 3 putts is to have better speed control on all your putts. Consistent speed at the hole allows you to always have a short putt for your second. Good speed control also allows the ball to take the break near the hole in a consistent way. In fact, it is almost impossible to become a great green reader without great speed control.
The best way to improve your speed control is to improve your rhythm. I have had so many students take the same length back swing for different length putts and try to guess the speed by whacking the ball harder or softer. This is and forever will be, a guessing game of speed. It is better to keep the rhythm the same and let the stroke length change with the putt length. It is much easier for the brain to tie a stroke length to a putt length than it is to tie a speed feel to the putt length.
Here is an example;
Imagine an orchestra conductor standing in front of an orchestra. They have that little baton that they move back and forth to the RHYTHM of the song. If the conductor wants the orchestra to play louder, the baton moves get bigger. If they want the orchestra to play quieter, the baton moves get smaller, but they ALWAYS move to the beat. This is how your putting stroke should work. bigger for big putts, smaller for small putts, but always to the beat.
Here’s how you do it;
Get a FREE metronome app on your phone and set it to around 85 beats per minute. Practice making putting strokes where you start your stroke on one beat and impact the ball on the very next beat. At first, you will struggle to start on time and it will throw you off. Eventually you will be able to anticipate when the beat is coming and start on time. As you putt, adjust the metronome to fit YOUR personal tempo. Once you find it, lock it in with practice. I like to setup a reverse ladder game where you stack 5 balls out from the hole at any distance you want. Start at the close one and move out. Each of the 5 putts should have the same rhythm, but a different length stroke.
Take it to the course by finding a TWO-SYLLABLE word that you can say to your beat. I use GOLF-TEC (shameless plug, I know). Start on GOLF, hit on TEC and do it the same every time. Once you find your rhythm, you will start leaving more putts close to the hole and stop 3 putting.