Good advice from Marissa
Just remember there is a difference between a horse responding to pressure, and as marissa replied, being rewarded - thereby learning, and a horse being forced about.
I could take any horse on the planet and yank it over in about 5 minutes - this will not teach it anything - and could lead to fatal injuries should the horse panic.
The key is to have the horse respond to a little pressure - be rewarded - and then left for another day - it can be a mistake to keep repeating the exercise over and over again. Slower is better ( and often faster ) , a horse can remember a previous exercise, and if repeated on another can make sure that you know the horse is remembering - not just repeating an exercise.
Little pressure, small movement, repeated over time can result in little ( or no pressure at all ) and a large movement.
I trained one of mine this way and ended up with a horse that would lay down by just tickling his elbow / girth area and asking him to ' lay ' - I also know that he remembered because the horse was found a couple of years after I sold him, his new owner ( who had had him for around a year ) had no idea of his 'special training' - she was told via e-mail how to lay him down, took him into the sand arena tickled his girth area , said lay and down he went .