I like some of Mark Rashid's ideas (pre-martial arts)
I would look into the ones who are not just out to make a buck (*cough cough parelli cough cough*)
^ agreed with staying away from the "carrot sticks"
Lookup Ray Hunt - that man was a real trainer who was downright amazing. He could communicate efficiently with the horse and with people he was teaching. There are still many resources to learn from on his techniques.