I'll tell you how it works for me. I'm not a trainer, competitor, or great rider, and I haven't had lots of lessons.
Although I'm more western in my approach, I like to practice riding two point (kind of standing in my stirrups, but with most of my weight going to my thighs). To be balanced in that position, you need your center of gravity to match the horse's. So if the horse is 'forward', you will be too.
Another exercise is one I got in my first riding lesson. She had me ride around a barrel, trying to keep the circle round. It wasn't pretty. Then she had me start a circle that way, and then settle back 'on my pockets' and bring my heels back, shifting MY weight to the rear. As I did so, the circle immediately became rounder as the horse also shifted to follow my weight. Doing it in mid circle made it very obvious.
You don't need lessons. It might help to have someone watch you and comment on how round your circles are, or your position. You can be back and still have a horse leaning forward...my mare is big on shifting her weight forward, probably because she loves running and straight lines, and hates circles and pivots.
I can't give advice on looking at pictures, because I'm wrong as often as right when I try it.
Off topic - the lady I took lessons from had no heartburn with someone asking to take 2-4 lessons so they could learn what they needed to practice on. Not all instructors are like that, but she gave my oldest daughter 2 lessons - one to assess, and one to give her things to work on.
The lady who trained our horses has also done that with me sometimes...I'd take 2-3 lessons when she had a regular student take a vacation. On a couple, she had me ride bareback with the horse on a lunge line - very interesting! A good instructor can teach you a lot in 2 lessons. For me, that was $60 well spent.
BTW - When I took up riding, I bought a horse that was advertised as "perfect for a beginner". If I had known more, the fact that they only allowed her to be ridden in a 30' round pen
, and wouldn't let me lead her anywhere
, SHOULD have been a huge warning! So for 4.5 years, the two of us have been learning together. NOT a good idea, but the struggle has been a great teacher. Just wish I didn't still have pain in my back from a tumble 4 years ago...