Joel Spolsky - How to demo software:

"As you go along, be sure to accidentally bump into all the nice little “fit and finish” features of your product. Oh look, that column is halfway off screen. No problem. I’ll just drag it over. (“Wha!” the audience gasps, “you dragged a column in HTML?”) Oh, look, this feature is supposed to be done by next Tuesday. I’ll type “next tuesday” in the due date box. (“OMG!” they squeal. You typed “next tuesday” and it was replaced with “11/20/2007”). Those nice little touches you put so much hard work into are not the meat of the demo, so don’t talk about them, just act nonchalant. What, doesn’t every web app let you resize and drag columns?"