First horse learns to turn his head toward the pull of a rope so if you
have a long lead attached under the halter and around say, his right
shoulder, you are holding it behind his left hip and give it a tug, the
horse turns around toward his right until he faces you.
Use that lesson and tap him on the appropriate hip that you want to
move away from the tap at the same time so he learns to yield to the
pull on the halter as well as away from the hip tap.
You can practice this standing by his side too, pull the head toward
you and tap the hip on the same side to have it move away from you.
Put the rope around the far side of his neck and reach over to tap the
hip on the opposite side, hopefully the result is the hip moves toward
you.
Then, when you are standing on something, and his/her hips move away
from you, you can reach across and tap the horse on the far hip asking
him/her to move the hip toward you and closer to what you are standing
on.
I hope this makes sense. It is a good excercise for winter training
when the weather is too nasty to ride outside.