Alan Alda has been studying ways to engage the public with science. He recommends the following:

Attraction – use body language, tone of voice, and eye contact more than words to grab audiences in the first two minutes.
Infatuation – use emotion, personal anecdotes, and stories to keep your ideas in the audience’s mind.
Commitment – maintain an ongoing connecting with the audience by listening and responding to what they’re asking.

For more information, surf to this article: http://spectrum.ieee.org/tech-talk/at-work/education/alan-alda-tutors-scientists-in-communication