Do Not Demo Naked
startupwhisperer.com
startupwhisperer.com
Our other professor, who was a) a genius and b) had some marketing skill, approached every product demo like it was the invasion of Normandy. He didn't just have it drilled to perfection, he had a Camtasia video of the entire thing drilled to perfection so if anything crapped out he could say "Whoops, technical issue -- now switching to the video of when I did it earlier today. As you can see..."
The article has some good advice. Also, remember to clear personal data from your web browser if you're demoing a web app.
Just another tip, create a demo user on your computer with all the stuff ready on the desktop (links, images, videos). It will more professional.