I don't use a lot or Powerpoint in my day to day practice, but I still get a tremendous amount of great ideas from Cliff Atkinson's Beyond Bullets weblog. A recent favorite post of mine is this one, where Cliff says:

Often a PowerPoint presentation can become so packed with bullet points, charts and graphics that we lose our sense of clarity, direction and focus.

But you can find your way back to your goals by mapping your content to the 6 primary signposts that underlie every effective communication experience: who, what, where, when, why and how.

It may sound basic, but that's the point. No matter how elaborate, detailed, complex and involved your story is, you have to clearly answer these 6 basic questions, or else you'll lose your audience, and your own understanding.

What great advice. Take a look at the post for a visual example using these signposts in a Powerpoint presentation.