K.I.S.S.

An oldie but a goodie via Garr Reynolds:

"Worried you're not using the right words? Use simpler words. Worried that your sentence isn't clear? Make a simpler sentence. Worried that people won't see your point? Make your point simpler. Nearly every writing problem you have can be solved by making things simpler.

This should be obvious, but people don't like hearing it because there's the assumption that simple = stupid. But it's not true; indeed, I find from personal experience that the stupidest writers are the ones whose writing is positively baroque in form. All that compensating, you know. Besides, I'm not telling you to boil everything down to "see spot run" simplicity. I am telling you to make it so people can get what you're trying to say."

— John Scalzi

This could probably be rule #1 for using visuals in your presentation. Keep it simple. Don't over think. Don't over produce. Just make your point as clearly and simply as you can.

Don't insult your audience by condescending to them. But don't try to impress them either.