7 guidelines to your first presentation

1. Tell stories. Seriously. People could care less about the five ways some XML vocabulary will enable enterprise whatever. Rather, put a screenshot of your project up, tell people what you learned while doing it, then give them a slide that reiterates those ideas in easy to digest bullets. That's do not go from bullet-point slide to bullet-point slide trying to tell people what to think.
2. Show pictures. Got a good metaphor? Use it. "The Web is like a school of fish." But go to images.google.com and type in "sardines" or "school of fish" or whatever. Make it a slide. Then say the Web is like that. Much more powerful and memorable.
3. Don't apologize. Ever. If something is out of order, or if something occurs to you as a mistake during the presentation, keep it to yourself. They'll never know. Besides, nobody cares about the presentation itself. This is really hard, because you know the whole backstory, and you'll be tempted to explain why something isn't quite perfect. Skip it. Also, you don't need to apologize about the color on the projector, or the fact that your mic just popped off your lapel, or that a staff person spilled a pitcher of water. Commiserating is fine, however. "If it gets another 5 degrees colder in here, I'll be able to see my breath!"
4. Start strong. I can't believe how many presenters forget this. Do not get up there and say, "Um, well, I guess we should probably get started." Instead, say, "Hi, I'm Jeff. It's really great to be here, and thank you so much for coming to my session. Today, we're going to talk about...." Make sure those are the absolute first words you say out loud. No need for a joke or an opening or any of that. Just start strong and confident.
5. End strong too. "...so that's why I like social software. I appreciate your attention today. Thank you." Then stand there and wait. Everyone will clap, because you just told them you were done. When they've finished, ask them if they have any questions. If nobody asks anything, break the uncomfortable silence with "Well, I guess I told you everything you need to know then. [heh heh] I'll be around after if you think of anything. Thanks again!" and start packing up your stuff.
6. Stand. Away from the podium. Out from behind the presenter table. Keep your hands out of your pockets. Take off your conference badge (the lights will catch it and be distracting). I pace a little bit around the stage, timed with my points, saying one thing from over here, and another from over there. But don't move too much.
7. Pause. When you say something important, leave a gap after it. Let it hang there for a few seconds. Try it when talking to your friends. "You know what I think? (pause...two...three...four...) I think Bush is bankrupting this country for the next twenty years. (pause...two...three...four...) Here's why..."