This is a putting drill I have used for over 30 years.
I start with a 3 foot putt, usually straight and level.
I call this drill, '30 in a row or you don't go.'
Here is how it works:
You have to make 30 putts in a row. Miss number 30 and back to zero, start over. I use 3 balls, because I want to have to pick the balls out of the hole often, as well as frequently going through re-gripping and setup.
Plus, this lets you stretch out and relax and approach each 3 ball set as a new putt.
I recommend that every now and then you use a chalk line to check putter face and setup alignment. (Note: a chalk line also works good for practicing breaking putts.)
All putts, even big breakers, are straight putts to the high point of the break. Set it up to the high point of the break. To practice looking, aiming and putting to the break point and not the hole.
Note: On Tour, before every tournament round, DJ usually goes to the putting green before the range. His caddy, Todd, always has a 6 to 10 foot chalk line (orange for Clemson) down and waiting for him. He will start putting anywhere from 3 to 6 footers and make a minimum of 30 in a row. I have seen him make 100 in a row from 6 feet.
That is almost statistically impossible.
PGA Tour stats show the players make, on any given day, 92% of 3 footers and 50% of 6 footers. That's a pretty big drop for just 3 feet ' an average of 15% for each foot.
My point here is to only try numbers that are reasonable and within reasonable statistics.
Considering those stats, I tell my students to start at a number they can do and then move up to 30.
(Note: be sure to watch the greens. If you stand in one place too long, you can wear footprints into the green. Superintendents will be rather upset about that.)
Once I make the 30 in a row, I drop back to 6 feet and the rule is make 2 out of 3, 10 times in a row. I don't care what order, just 2 out of 3. When the 6 footers are done, drop back to 9 feet, where you have to make 1 out of 3, 10 times in a row.
Then I drop back to 12 feet, 15 feet, 18 feet and lastly 21 feet. From 12 to 21 feet, I am looking to be sure and reach the hole every time.
As Dave Pelz, the great putting coach, says, you should imagine hitting it at least 12 to 15 inches past the hole, since that is the optimum speed/distance for putts to hold the line and go in.
This exercise for 3 feet to 21 could take an hour or so.
I do not do it every day from 12 to 21 feet. I do the 3 – 9 feet quite often. If I am pressed for time, I only do the 3 foot test, which I also make it a practice to do before playing any tournament round, and sometimes after.
The degree of doing these is based on your need to do them and your time.