Refine and hone your presentation so it's on target, clear, and interesting. Keep it short. Ten minutes. Long will kill you; short will bring applause.
Make your visuals interesting. Get help. Bullet points and PowerPoint slides made up entirely of text won't do it. They're boring. Use pictures where possible.
Know your content cold. If you drop the ball when challenged, you're dead. Your credibility will evaporate.
Start slowly with the thought that you'll pick up the pace later. This never happens! If you lose your listeners early, you won't get them back.
Hand out copies of your slides beforehand or your listeners will concentrate on those instead of on you during your presentation. You don't need the competition.
Stray from your prepared talk. If interrupted, ask your audience to write down their questions as they come up so you can address them at the end.
Talk too much. Instead, surprise your listeners with succinctness, not length.