1st step: Get a carrot, treat, apple, etc.
2nd step: up your horses leg and say "Shake". Give him/her the treat.
3rd step: then go to tapping his/her shoulder until he give you his leg. Then give his the treat.
4th step:Now start tapping his knee until he gives you his leg as your saying "Shake".
5th step: keep doing this for a few weeks then eventually all you say is "shake" and he will give you his leg :)
Any questions ask. I also have tought a few of my horses how to "dance" I guess you would call it ha, so if you wana kno how to do that..Ask :)