Post from your knees not calves and ankles. It's hard at first but it makes all the difference. Also don't for get to keep your back straight and shoulders back.
When you sit for a post, pretend like you have a baby bird under on your saddle- you don't want to post to hard or fast to crush the baby bird.
Tight with all your leg!
Also keep your back soft :)
*so I was sort of scared to stand up. Just keep your knees bent slightly. Don't brace the reins or with your knees. If you feel unstable, practice at the walk first, then trot, or even at a halt before you are comfortable posting at the trot.
Hope this helped:)
My instructor told me to rise and fall with the (front) leg closest to the wall.
Keep your heels down as shock obsorbers and try to fall softly.
If your horse speeds up, don't go with the horse, but instead, post slower. Then the horse will have no choice but to slow down, because they can feel you in and out of the saddle.
When I first started English riding, I wasn't used to the stirrups being so short so it