AZHT: Teach a Horse to Stop at the "Whoa" 

Teach your horse to stop at the "whoa" and back up all in one transition. This sets them up when you want to roll back or turn around and pivot it on that hind. You want to teach them this at a walk first before you go to the trot or lope.
As always it takes time, patience, and practice!
Soft Hands, Soft Horse!