Begin by appealing to the oldest part of your audience's brain...
You have the most critical, game-changing information on the planet to talk about, but if you don't immediately create a connection with your audience, your message will fall flat.
As speakers, our message is dependent on our audience's openness to hear what we have to say. That openness, however, is controlled by structures deep in our brains that make snap judgements about a person's trustworthiness and authenticity. This neural judge and jury is a lightening-fast attribute that helped our ancestors survive, and it continues to control our trust in other people.
Fail your audience's preliminary "comfort test," and you've already lost connection. And without a connection, your carefully crafted message, complete with painstakingly constructed evidence and analysis, won't move your audience to action. It won't move them at all.
Along with the primacy effect, this makes the opening seconds of your presentation absolutely critical. How you walk on stage, your initial interaction with the audience, your posture, facial expression, and how you deliver the first few syllables (regardless of what you're actually saying), all set the stage for your message's reception. As a general rule, the more you positively acknowledge and present to your fellow human beings, and not a generic mass audience, the better your connection.
So the next time you prepare a presentation or keynote address, pay particular attention to the opening. While all components of a presentation are important, the wiring of the human brain proves the old adage, "You never get a second chance to make a first impression."