Here are some general pointers for PowerPoint slides:
- Use images wherever they can replace words
- Keep the slides simple and neat - don't overdo the text
- The font size should be at least 28pt (I try not to go smaller than 32)
- Use contrasting colors (black text on white background or vice versa)
- Do not use too many colors or too much of one color (overusing red makes it lose its impact)
- Print out a notes page of one of your slides. Put it on the floor at your feet. If you can't easily read it when you look down at it, there is too much content and your font is too small.
- Don't overdo animation - keep their focus on you
And remember, PowerPoint isn't the only kind of visual aid. Don't discount a row of flip charts that you can write on (largely), white boards, magic tricks or anything else you can think of that can add a bit of fun to your talk.