The following works perfectly if you are using the standard distance formula, are a "dead ball" putter and use the ding approach. It will get you very close. It is a good STARTING point as you have to adjust slighty to wind, varying slopes as ball travels, effects of break at end of putt versus beginning of putt, etc. I use reverse view to gauge breaks.
The break is 1 square per 10feet from hole(straightline distance, not adjusted distance) for very fast beads.
Of course you have to recognize what very fast beads are. Anyway, adjust from there, i.e. medium moving beads break is 1 square per 20 feet.
My personal problem is that i dont/cant ding as much as i should, so i have a lot of 8inch putts, but I am ALWAYS close regardless of distance from hole.
So as an example on a 30 foot putt. Slow beads for the first 10 feet, very fast in the last 20 feet. Break would be 2.25 squares.