Opening the book…
The divot is the only permanent record of where your low point actually was, and it does not lie the way feel does. A divot that starts behind the ball means you hit ground first and the ball got whatever energy was left. Reading divots gives you a scoreable check every single swing without any equipment.
Place a coin, tee, or short stick beside the ball to mark the original position, hit the shot, then look at where the turf broke. You want the near edge of the divot forward of that marker, with the deepest part further forward still. Also check direction: a divot pointing well left or right of your target line tells you the path needs work before the strike will settle.
On firm, dry, or mat-covered surfaces you will get a scuff rather than a divot, so judge by the mark's position instead of its depth. Do not chase divots at the expense of contact — a shallow brush that starts forward is better than a deep gouge that starts behind.