Teaching a horse to stand for mounting is as easy as getting it motivated to want to do so.
This clip isn't the best quality (filmed with a mobile phone) but one can see what's going on. After I show how to get started one of my students takes over, and a few minutes later the are on a roll. The horse, a two year old mare, hasn't tried this before, but she catches on fast.
The rules of the "chair game"?
If the horse can catch the person and gets in the right position, she wins the game. Can't get the scratches if one stands too far away; a concept understood by all horses with a scratch :)