Agree! Video has helped me see what I need to work on and I take time to focus on that certain thing! If you have strong legs that helps too because you can hold yourself in a better position! I think it depends on what you are having trouble with as well, such as are you getting ahead of your horse, falling behind, grabbing mane, ( not a HUGE problem) is your leg getting really far back, and so many more! Figure that out and focus on it! It will help!
Ask someone to take a picture or a video of you jumping.Something that helped me is practicing my two point at a halt, walk, trot than canter. You can really feel your position before taking it to a jump. Hope that helps. xx
Riding bareback a lot really increases your balance. Since the jumping position depends all on balance it is a great way to improve that too.
Another way is riding and jumping while being lunged without the reins. This will help you achieve again balance but with the independence from the reins. I