Most amateurs look up after an iron shot and read the ball flight for clues, which is a bit like reading a weather report after the storm has already passed through. By the time the ball is in the air, the information you actually need is already behind you, sitting in the turf, and almost nobody bothers to turn around and look at it. A divot does not lie the way a single shot sometimes can. Hit one bad shank and the divot might tell you nothing beyond a mis-hit, but look at a handful from a single range session and a pattern appears that is far more honest than how any individual shot happened to come out.
Start with where it points
Lay a club down along the line of your divot, from where the club entered the ground to where it left it, and compare that line to your target line. A divot that points noticeably right of target, assuming a right-handed swing, usually means the clubhead is still moving across the ball from out to in as it strikes, the classic over-the-top pattern that produces a pull or a slice depending on what the face is doing. A divot pointing left of target tells the opposite story, a path coming too far from the inside, which on its own is not a fault so much as a tendency that needs a face angle to match it or the ball starts leaking well right of where you aimed. Neither direction is automatically wrong. What matters is whether the divot direction and your actual ball flight agree with each other, because when they do not, you are usually compensating for one fault with another and masking both.
Depth is about more than digging
The second thing worth checking is how deep the divot is and where the deepest point sits relative to the ball. A proper iron divot starts at or just ahead of where the ball was and gets progressively deeper moving toward the target, shallowing out again a few inches further on. If the deepest point of your divot is behind where the ball sat, you are hitting the ground before the ball, which is the fat shot you already know about from the strike, but it also tends to show up in a flatter, lower ball flight that loses distance in a way that is easy to blame on the wrong club rather than the contact. A divot that barely exists at all, a scuff rather than a proper slice of turf, usually means the club is bottoming out before it reaches the ball and rising again by the time it gets there, which is how thin shots and toe-high contact happen even on a swing that looks reasonably sound from the side.
No divot can be its own problem
There is a particular amateur pattern worth naming on its own, which is the golfer who takes no divot at all and is quietly proud of it, treating a clean strike off the top of the grass as proof of good technique. With a fairway wood or driver off a tee that is exactly correct. With a mid or short iron, it is usually a sign of scooping, the hands and the club trying to lift the ball into the air rather than letting the loft of the club do that work through a descending strike. Good iron players take ball, then turf, in that order, and the divot is the physical proof that the strike happened on the way down rather than on the way up. If your irons come off the turf clean every time, that is not a technique worth protecting, it is a pattern worth testing against a bucket of balls and an honest look at what is actually happening at the bottom of the swing.
What to actually do with this
None of this requires a launch monitor or a lesson you cannot get booked for another fortnight. Hit ten balls off the range mat, or better, off real turf if you can find a strip of it, and resist the urge to glance at the ball flight first. Look at the ten divots instead, lined up next to each other, and ask whether they agree on a direction and a depth or whether they are scattered all over the place. Scattered divots usually mean an inconsistent strike before they mean an inconsistent swing path, and that is a different problem to go and work on than the one you were probably planning to fix. A consistent pattern pointing one direction, on the other hand, is about as clear a lesson as golf gives you for free, and it was sitting on the ground the whole time, waiting for someone to actually look down.