I just listened to this terrific interview with Mark Bowden on the power of body language:
Bowden gives simple tips for ways to build audience trust. For example, he explains that if you tilt your head slightly towards the the audience while you speak, the audience will be able to see your ear and thus feel that you are listening to them - even if you never stop talking!
From the Green Room: Don't assume that your words are sufficient to gain the trust of your audience. If your body language doesn't communicate your trustworthiness, even the most sincere speech will raise the suspicions of your audience.