Decide on a focus. If you are well-known for something specific, your audience will, no doubt, expect your speech to be about that topic.
Put yourself in your audience's moccasins as you write. You want to connect.
Keep the speech to two or three major points.
Find your voice - perhaps warm and conversational, sober and profound, vigorously controversial, or wise and understanding.
Write an outline with your topic statement and the critical points as headings.
Fill in your transition spaces with anecdotes, quotes, even relevant jokes to ensure your speech will be unique, interesting and audience-aware.
Draft your closing remarks.
Write a completed speech as tight or loose as fits your style.
Practice reading the speech first for time.
Practice again for cadence and delivery.
Read aloud with any hand motions or movements you intend to incorporate.
Create the props you'll take to the podium - notecards or the full speech, double-spaced and typed.
Try your speech out on a person, especially one similar to the folks in your intended audience.
Relax. You'll be great.