You have to have the right equipment, I see a lot of vaulter starting with cheap surcingles and saddle pads, which are not adapted. You also need a good horse, who turn well on the circle, who doesn't rush.
You need to try to go everywhere on the horse, forgetting the surcingle. You have to train on the three gaits, start with walk, then trot and finally canter. You learn a move on a walking horse, then you trot and after you canter.