Top notch guide I can attest to it as a person who has been horse riding for 5 years now.
I also stress the importance that EVERY horse is different. I personally own an alpha mare and she is a prissy horse and is irritated by anything that isnt eating, sleeping on the pasture or the occasional slap'n'tickle :3
I would also add, although its something trivival, that horses when itchy like to scratch themselves on things. If a horse is try to run its head/butt against you it feels secure around you.