lEYE CONTACT
One of the most oft-metioned components of facial expressions is eye contact. Looking audience members directly in the eye allows you to connect with them on a human level. Strong eye contact communicates sincerity and confidence and shows that you are engaged in what you're saying. It also makes it more likely that your overall facial expression will be appropriate. The goal is to meet an audience member's eyes for 3-5 seconds and then move on to the next person. Try not to "sweep" across the audience, don't favor one section of the audience over another and keep your pattern of eye contact random so you're not continually going from right to center to left and back again.
THE SMILE