Do you: come towards him with your hand out? Palm up or palm down? From the front or off to the side? Pat or rub his face, forehead, or shoulder first?
I have heard all of these, plus, just stand in front of a horse and let him come to you first, but then I also heard, horses are not dogs, they do not need to come up to you to sniff you.
My instincts always have me coming from the side, palm down to let them sniff my hand.... maybe I've been a dog lover too long, and need to change things with horses?!!! Lol!