Michael Grinder, one of the gurus of body language and non verbal communication talks about different things that people do in their non verbal communication that will make them appear approachable or credible. Clearly at different stages of a speech you will want to be approachable. But at other stages, you will certainly want to be more credible. So knowing these aspects, will help you be more effective when you communicate.
I have summarised the key aspects from Michael Grinder in a PowerPoint slide for you.