I taught my gelding how to bow, shake hands (hooves
), say yes and no, and stay. I'm working with him on come, consistency with yes/no in questions, as well as follow, smile, and hug.
My advice be patient and realize that not every trick is suited for every horse. (I.E if your horse has a pawing problem then it probably isn't wise to teach the horse to count, etc). Also, make them realize that you have to cue the trick, they can't just do it whenever and get the treat. In my limited experience that's the best way to nip any bad behavior or dangerous ones in the butt. :)
I know on youtube there's a girl from.... russia? I believe who does trick training and I love her methods and explanations. If I can find her vids I'll post one. :)