Practice is the thing. Toastmasters is wonderful for this, however much it may seem like a relic. You'll never have the speaking fast problem if you go to Toastmasters. They catch that early and let you know.

Jonathan's tip of mentioning you're nervous. Big no-no. They know you're nervous, and they don't need you to tell them. Or they don't know you're nervous, so why give away the secret.

Pawliger on demos: Never do that, especially if there's an online component. Save screenshots.

Recording your speech is essential. Video is great if you can do it. You dread it like the plague, but you'll be relieved that you aren't as bad as you thought.