Gaining eye contact - the face and body as well - means people can see what you are saying matches what you actually think. This type of analysis is understood intuitively by some but there is some science behind the gestures of which the work of Paul Enkman is most interesting ~ http://en.wikipedia.org/wiki/Paul_Ekman TV watchers might recognise his work in "Lie to me" ~ http://en.wikipedia.org/wiki/Lie_to_Me

The "handshake" and "hug" serve numerous functions, one I've always found interesting is the "oxytocin" hack ~ http://www.psychologytoday.com/blog/the-moral-molecule/20081...