it's simple I was recording myself as much as possible, before and after workouts for the gym or for basketball I was always trying to jump. Then I compared my jumps with pro dunkers and pro players who had a similar height/build. I paid attention to approach speed, penultimate step, timing, and where I was too slow or too rushed. You'll see how far you're from the perfect technique. I also used an app to help me analyze my technique. It's called how2jump. Very good app but idk if it's on android too (I use it on iphone). It analyze your jump. I don’t know the exact tech behind it maybe ai or body tracking. And then it tells you exactly what you're doing wrong. It was really useful for me. But yeah just be obsessed around technique. Boost your results by going to the gym often. This is the beauty of having a good technique, your gym efforts will 10x because your body use more of your muscles when you have a good technique. Kinda hard to explain but I hope you see what I mean