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After rehearsing onstage demos with fifty companies last week, TechCrunch50 conference organizer Jason Calacanis listed eight rules for giving a good demo in a message sent to his public mailing list. What's the worst thing that presenters do deliberately? If you've ever been to a conference, you'll recognize it.Many presenters believe in repeating their message three times for the audience: "Tell 'em what you're gonna tell 'em. Then, tell 'em. Finally, tell 'em what you told 'em." It's a practice that comes from academia, where summaries of long, complex research papers help make them digestible. Calacanis hates that:

Your script should never sound like this: —> "With YouTube, you can upload videos, tag them and share them with your friends." —> "Here we are uploading a video, tagging it and sharing it with our friends." —> "We just uploaded a video, tagged it and we shared it with friends." It's like kissing a cute girl and saying "I'm going to kiss you," "I'm kissing you" and "I just kissed you." If you have limited time—and that is the case 99% of the time—I suggest just showing the product doing its thing.

(Photoillustration by AllThingsD)