Stop wasting time at the beginning of a talk to introduce yourself, explain why you were asked to give a talk, list an agenda of what you want to talk about, make a poor attempt at a joke. Instead, jump in and get on with the content.
This video, of a very short TED Talk, is a perfect example of how a cold opening can grab the audience's attention right from the beginning. You'll always have time to do those other things later in your talk, but the first 30 seconds are so precious, why waste them?
Sebastian Thrun: Google's driverless car | Video on TED.comhttp://www.ted.com/talks/sebastian_thrun_google_s_driverless_car.html#
Sebastian's talk has all the elements of a great opening, and follows Garr Reynolds' instructions to start your presentation with PUNCH. It was a personal story of his interests as a boy, an unexpected turn of events when he lost his good friend to a car accident, a novel way to look at the challenge of automobile travel, presented a challenging problem to overcome, and was humorous in its delivery.