I got to talking with some friends about how to deliver a presentation very smoothly without tripping up on what one wishes to say. Because as is often the case, one has a lot to say, knows how to say it, but sucks at delivering it. Anyway, one of my friends shared with me that the nervousness is mostly what ruins the delivery of some subject matter by one who most likely is quite knowledgeable of what they wish to convey. So her suggestion was to imagine that one is delivering the speech to their best friend in the entire world--the audience becomes that best friend and everything thus flows smoothly. I've tried this, and I've found that it works better in dimmer lighting or better yet a dark room.
That works. For me, being passionate about my subject is important. But it can't be too engrossing, or I will start talking too fast and stumble over my words.