I've taught a lot of foals to lie down (which is easier than full grown horsies) but its pretty simple to teach a horse to lie down. If you type "How to teach a horse to lie down" into google, you'll most likely find an answer..
How I did it:
1. Halter the horse and hang the lead over his back from the right side
2. Stand on the horse's left side, where the end of the lead rope is
3. Pick up the horse's hoof while you're FACING FORWARD (facing backward might make him think you're cleaning his hooves and the next time you go to pick them, he'll try to lie down) and loop the rope around his leg so you have a firm hold on it (and your hands aren't in between the legs and the ground)
4. Hold the part of the lead rope that's over the horse's back with your right hand and with your left hand, hold his leg up
5. Gently pull back with both hands, pulling his head back and bending away from you, and pulling his leg back
6. The second the horse's body starts to shift in the direction you want, release all pressure, let him have his leg, and reward.
Every time, ask for a little more, and every time he gives, you release. Soon, the horse will drop all the way to the ground.
While teaching Leia, I'd say "Down" in a low voice and poke her shoulder while I pulled her down. Now, If I'm on her, all I do is touch my toe to her shoulder and say "Down" and she'll start to go down.
Good Luck! And Happy Holidays!
-Charlotte & Leia
“Have fun - Stay on top.”
"There's nothing like sixteen hands between your legs"