How do you develop a horse's ability to be ponied from another horse?

Ponying — leading one horse from the saddle of another — is a practical skill used to pony young horses alongside experienced ones as part of their early education, to exercise multiple horses simultaneously, and to manage horses in field or trail situations where leading from the ground is not practical. For the horse being ponied, the experience introduces concepts of following alongside another horse at various gaits, accepting contact from a rope attached to its halter while in motion, and moving forward and sideways on command from a handler who is not directly on its back. The first ponying experiences should be conducted at a walk with a calm, reliable pony horse and an experienced handler in the saddle. The young or inexperienced horse should already be comfortable being led from the ground at all gaits before it is ponied, because ponying introduces the additional complexity of motion and contact while in motion. The rope should be held with enough length to give the horse room to move alongside without feeling restricted, but short enough to maintain control if the horse attempts to pull away or drift. If the horse pulls back or resists, the pony horse moves forward steadily while the handler maintains consistent contact rather than pulling back against the horse — the forward movement of the pony horse creates a consistent pressure that the ponied horse learns to yield to by moving forward. Ponying at progressively faster gaits is introduced as the horse's comfort and responsiveness develop, and the ponied horse gradually learns to maintain position alongside the pony horse from light rope communication.