When you have your goals set you can finally get to PowerPoint, right? Lots of people begin building their presentation at this point. Don't. The problem with slideware is that you get to the very small details like font size or diagram setup too soon, and thus you lose the big picture. After about 30 minutes of struggling with colors, you don't remember what you want to say.
Don't start in a word processor either. A word processor ultimately forces you to think linearly and you need to think hierarchically first. I know this sounds cryptic, so let me explain.
Stories are linear. They have a nice flow, a sequence of events, one after another. Slides or a cinema tape (which is essentially the same thing) is a good metaphor for the story: one thing after another and another. That's how the audience sees the story, but that's not how the author (or presenter) sees it. For the author, the story is a hierarchy! Have a look at the Figure 2-4.
The audience doesn't need to see the hierarchy. Even though some presentation software exposes the underneath hierarchy (most famously, perhaps, www.Prezi.com), I don't see the reason for this. It confuses people and makes them think about the presentation's ...