When you stand behind your horse you should do what?

Unless you are 6 feet back or at least out of leg range, you shouldn't be standing behind your horse at all. If you must stand behind your horse, always be sure that you are far enough back that if your horse spooked, it couldn't kick you. You should also let the horse know that you are behind it so that there is less chance of it spooking and hurting you. And of course, obviously, don't try to walk behind a horse that you don't know well. Without being familiar with the animal, you would have no idea what to expect from it.