"A picture is worth a thousand words..."
... but it's a different thousand words for each viewer!
So try to be clear about describing what you see.
Good: "So after I click the submit button, you'll see a spinny animation for a second... <click> There it is! <click> ... and now the next page is loaded."
Bad: "<click> Did you see that spinny?"
"Better to remain silent and be thought a fool than to speak and to remove all doubt."
Awkward silences are great for eliciting feedback and gathering information. The audience members will feel awkward too, and will want to fill the void.
...and it's not a demo unless something goes wrong
Relax. Make a self-deprecating joke. Take a deep breath. Remember that the audience is on your side.
iPhone Launch by Steve Jobs: https://www.youtube.com/watch?v=x7qPAY9JqE4
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