Reading the breaks is the most difficult of all skills to acquire in this game. It takes lots of practice, and keeping notes is very helpful.
A few tips:
A downhill putt will react more strongly to the break than an uphill. And the faster the green speed, the greater the break.
Note where on the path the break occurs. It's counter intuitive, but a break nearer the beginning of a putt will have a bigger impact than a break near the end.
It is useful to look at a putt both from the standard view and the reverse view. I generally hit the ball from the reverse view.
If you pull the pin, it will give you a better look at the putt.
If the break is confusing, switching to chip mode will give you a simpler look at the break. Once you read it, switch back to the putter.
Many new players develop a bad habit at whacking the ball to take the break out of the picture. While you can get away with this some on slower greens, as you advance it will cause you more grief.
That said, a little bit too firm is better than a little too soft. Nothing worse than missing a putt two inches short that would have been dead in the hole with just a little more speed.
I'm not a "formula guy." There are players here who are the equivalent of rocket scientists. But these tips are based on a lot of rounds played. Hope they help.