Was just out with my brothers Dakota and Sterling. Dakota is a 4 year old American Mustang, and Sterling is a 5 year old Tennesee Walker. Dak told me to write this. He wants everyone to know Horse Language!
When meeting a horse for the first time, put your face down to their nose and they will do the same. That establishes dominance, and what I do is do nothing, because that tells the horse you are both equal.
If you have a bond already, offer the horse your shoulder. That is the equivalent of the withers, and is where they groom each other; it shows appreciation. If the horse is your's and you are his, as Dakota and I are, stand near them, lean against them, and (this is instinctive; something you just want to do with a horse) put your shoulder under their head.
If a horse does not show interest in anyone, and if you want to show affection, walk by him and brush against him. (Thats what Sterling demonstrated)
And just trust your instincts, and trust yourself.
Remember to keep in touch with every creature you meet in some way, whether it be meeting with them a lot or a small energy string between you. It will pay off in the end, trust me.