I've been given the advice that I need to be comprehensive so this is my attempt. I realize that someone has already posted a node about how to greet someone in Korean(by saying "an nyung hah sae yo").

However there is a physical aspect. One must always, when greeting an elder, keep both legs straight and together, put both arms stiffly by your side, keep your back straight and bend from the waist. Keep the head down and do not look at the elder. Then, of course, lift yourself back up. While bowing, say the greeting. Do not bow too slowly nor to quickly. It's a cultural thing that everyone who lives there has to learn.