Sitting Trot...?

Troting is a side to side movement not an up and down one. The best advice I ever got was to try it and then transfer that feeling into your movement while under saddle. I know it took me awhile not to bounce but it is actually easier to learn without the saddle. The other advice I got that helped was to pretend you're on a bicycle and kind of "peddle" it's sort of hard to describe in works... easier to demonstrate!! Anyway Good Luck and keep practicing.