I've been training Montana to do some tricks lately, and liberty training. It's really fun, and I thought it's be neat to have her smile on command with her upper lip. Here's how I taught Montana and Sheba to "smile."
Start with treats. You'll want to stand on something high out in your horse's pen or pasture so they have to reach up for the treat with their upper lip. I stood up on our trampoline, and also on a plastic 50 gallon barrel. Hold the treat up so that your horse has to reach up for it with her lip. While holding the treat up just beyond reach, say, "smile!" in a happy voice, and as soon as your horse twitches her upper lip and reaches for the treat, praise her and let her have the treat. Repetition, patience and timing are very important. The instant the lip reaches up, feed the treat and praise your horse. She will soon get the connection that you want her to put her lip up.
Have fun!
~ Grace