Rehearse. Don't try to memorise the whole thing, you're not a trained actor, but work on the important parts so that they'll come to mind when needed, and you can fill around them.
Speak slowly.
Speak clearly.
I always start by staring at a point on the far wall just above the highest head and then slowly bring my gaze down. If you're making a speech asking for funding or similar, make sure that at least once in the speech that you look at the dignaties, and look them in the eye.
Believe in what you're saying...
Good luck, public speaking isn't difficult, it just needs a little confidence.
