Know the room. Be familiar with the place in which you will speak. Arrive early, walk around the speaking area and practice using the microphone and any visual aids.
Know the audience and the organization.. Greet some of the audience as they arrive. It's easier to speak to a group of friends than to a group of strangers. Be prepared to have dinner, chat, and be at ease.
Know your material. If you're not familiar with your material or are uncomfortable with it your messga e will be les clear. Practice your speech and revise it if necessary.
Realize that people want you to succeed. Audiences want you to be interesting, stimulating, informative, and entertaining. They don't want you to fail.