Vanessa Van Edwards is a human behavior investigator, and in her charisma talk, she discusses the importance of a seemingly simple and yet crucial mannerism: hand gestures. As far as charisma is concerned, hand gestures have an incredible influence on the speaker's ability to persuade and captivate.
By way of an example, she points to an analysis of TED Talks. In her research on the popular online videos, she found that the most successful TED speakers used an average of 485 hand gestures over the course of their 18 minute speech, while the least successful (both metrics considered in terms of total views) used an average of less than 250.
There are other aspects of human behavior that influence how people are perceived, of course. Facial expressions are just as important. Van Edwards specifically looks at what are called "microexpressions": small, involuntary facial expression that follow intense emotional reactions. There are seven universal microexpressions that translate across cultures, and Van Edwards teaches about four of her favorites.