braiding the mane and tail

Usually you'll only braid the mane and tail if it's for an event or show, since it takes a few minutes.
Do it as if you were braiding your own hair. When doing the tail it can be more hard because you'll have to get directly behind the horse. You'll need to have someone holding the horses reins in front and someone on the side to calm the horse. Don't be afraid to pull the mane a bit if you need to, because it won't hurt the horse.