When people are forming an impression of you, only the words you say account for only 7% of what they take away; during this intriguing body language speech Deborah Gruenfeld talks about the importance of acting appropriately.
People don't think about mechanics of the body language of power. We learn this power through socialization. When we need to show someone respect, we naturally do things differently than when we need to take charge.
During this body language speech Gruenfeld talks about authoritative body language versus approachable body language. She says that both are equally important for success but each needs to be deployed at different times. For example, authoritative body language should be used when you are trying to show control. You should hold your head still and speak in full sentences while trying to show no viable reaction to what other people are saying. Conversely, when you need to have approachable body language you should take up little space and smile when other people are talking.