I copied this from another site- Yo Yo game:
The Backward “Yo”
First draw a circle in the dirt around your feet, about three feet in diameter. This is your own invisible corral — don’t move outside this corral!
It’s important to keep your feet still; it’ll help you learn how to move your horse without you moving. Your horse will respect you, because horses play the game of “who’s moving who” with each other, and by staying inside the circle, you’re the winner!
Your lead rope should be about 12 feet. Stand in your circle and drive your horse backward about three feet (Driving Game in the last issue). The middle of your rope should lay on the ground. There are four phases you may need to get your horse to move backward in the Yo-Yo Game.
Phase 1: Hold the end of the rope in one hand and place your other hand on your hip, so you’ll look like the boss!
Put a really stern look on your face, then wiggle your finger at your horse and think “back up!” If he takes even a half step, stop immediately and smile. He’s trying! Start again until he’s backed up about 10 feet. After he’s backed all the way, reward him by letting him stay there for a minute or so.
Remember to reward the slightest try. When your horse takes even a tiny step backward, stop immediately, smile, then begin again. He’ll try even harder for you the next time.
If he thinks your finger wiggling is silly, try this (Phase 2). Without moving your feet, hold the rope so that your fingers are closed around it and you can see your fingernails. Wiggle your wrist from side to side, which will cause the rope to move. If your horse still doesn’t back up, proceed to Phase 3.
For Phase 3, bend your arm at the elbow, stiffen your wrist and swing your lower arm from side to side in front of your body. Keep your elbow bent! Your horse should be getting the message now! This motion allows him to feel the wiggling rope all the way to the snap. When he does respond, quit. If he doesn’t respond, try Phase 4.
For Phase 4, straighten your elbow so your whole arm moves straight out from your shoulder. (Are you still inside your corral?) Send big, sweeping waves down the rope by moving your straight arm across your chest. By now your horse will really want to move backward!
Our goal is to have your horse respond at Phase 1: Point at your horse and he backs up.