Find somebody with terrible eyesight, and see if they can read your deck. If they can't (probably because your colors are bad, you have too much text, and/or you're being cute with fonts), fix your deck.

Turn off your phone/IM/notifications. Seriously.

Don't bring up anything you aren't going to explain--it just distracts people. Think of it like leading people through a house--if you show a door but don't open it, they'll be preoccupied with what's behind that door when you're making your next important point.

Never do a live demo without screenshots and videos as backups, just in case. Never let somebody from the audience help you debug things--just kill it and move on.

Your audience has no idea what you're going to say, so don't worry about fucking up mid-sentence or pausing too long--most everyone will totally miss your hiccup. They will remember if you screw up, backtrack, and look visibly shaken.

Don't read off your deck don't read off your deck don't read off your deck.

~

These are things I've seen students and people new to pitching screw up on a lot.