Making me squint gives me a headache
If people have to squint to see your graphics or your text, they won't. They'd rather check their Blackberries.
Everything may look nice and dandy on your personal computer before the presentation, but your audience needs to see your work across a crowded conference room. Always go bigger than you think you need to. Small text will help no one.
Black background + dark text = waste of time
Have you ever printed black ink on dark paper? How about bright yellow on neon green? Probably not. Why? It sounds ridiculous since the whole point is to read what you have.
Despite how obvious this seems when talking about printing on paper, it's amazing the number of people who told us about PowerPoint presentations with text that didn't have enough contrast to be readable. If it's not easily readable, then it's a waste of time.
Make sure, if you use dark text, use a light background -- and vice versa.
Don't read to us
Putting your entire presentation up on the screen, and then reading to your audience is no fun for anyone. You'll just end up tripping on your words as you monotone read to a bored audience.
Just project a snippet or bullet. Then, explain what that bullet means.
This will keep your presentation moving, and it will keep the rest of us from snoozing or continually checking our watches.
Pick your template wisely
Let's face it, every day we mock at least one person's outfit or ability to match colors. Heck, Joan Rivers has made a career of it (somehow). There are few among us who can design well.
When you're making a new presentation, find professional designers, and ask them to create your templates. Don't try to make them yourself.
Bad use of colors or fonts can make the presentation unreadable and can distract terribly. If you can't find a good designer, use a basic, pre-made template with very few flourishes. It's better to use a bare template, than an eye-jarring one.
Give us handouts
Would you rather your audience furiously scribbled notes or simply wrote a few points here and there in the margin?
If you give a handout before you start, the audience can follow along easily while watching you. You want the audience taking in what you're saying, not chicken scratching on notebook paper.
Leave animations to Disney
Animations and scrolling text often seem childish. Leave them out, if you can.
Everyone is there to see you, not some awkwardly moving something-or-rather. Make people remember your point, not the cutesy thing you found online and added in there.
Everyone needs an editor
Make everyone remember your content, not your mistake. Always take a few minutes to re-read what you have. Find at least one other person to follow behind you and double-check your work.
KISS: Keep it simple, stupid
Each slide should guide the conversation -- not be a jumbly distracting mess. Make each slide about one salient point, not the contents of your brain dumped out.
The simpler the slides, the easier they'll be to understand. The more complicated the slide, the easier it will be for your audience to check out and ignore you.
Properly label your graphics
Graphics are great, if you don't mess them up. You need to make every attempt to not give stupid-question-boy-in-the-back ammunition to ask what the red upward arrow means.
Make sure you label both axes and give the whole thing a title. Otherwise, you'll be derailed and have a hard time getting back on track.
It's a performance
The whole presentation is a show, and you're the star.
People will be staring at you and just glancing at what you have on the screen. Prepare early, and go through what you want to say and how your PowerPoint slides will help you during the process.
The better prepared you are, the better your information will be received and retained.