My previous farrier always clued me in to what he was doing to my horses' feet while he trimmed. He told me that a horse should strike slightly toe first at the walk, midfoot at the trot/running walk, and slightly heel first at the canter or higher gait. He was a nationally renowned farrier- he was flown all over the country to dressage barns for grand pre horses twice a year. =o
He was also showing me how a TWH should be trimmed. I don't know if it's different for a non-gaited breed, but it seems like it should be the same.