When speaking to a large group, sweep the audience with your eyes slowly and at regular intervals. Watch for faces that provide feedback, and pause occasionally to gaze at individuals in the audience. This improves comprehension and interest on the part of people in the audience. Holding your arms crossed over your chest indicates a closed, inflexible position. Stifle or cover a yawn whenever possible.
Silence is a communicator.
A pause punctuates or gives emphasis to words. But a long silence may be a turnoff. People tend to face each other as directly as possible when they are interested in what is being said. They also nod or smile from time to time. People who lose interest in your conversation may change positions, break eye contact, swing their feet or tap their fingers.