MR pointed me to this entry on how to give a talk. The part I liked best (esp. #1):
The Big Four
A collection of four heuristics that make a talk work.
1. Cycling. Deliver ideas first in brief, then in detail, then in summary. To use the lingo of artificial intelligence: let your audience load the schema, then fill in the details, then let them know what’s worth indexing for future reference.
2. Verbal Punctuation. Provide a mechanism to help people who “fogged out” to easily rejoin the talk. For example: “We have just finished talking about the first heuristic, cycling, I am now going to talk about the second heuristic for helping to make your talks more interesting…”
3. Near Miss. When explaining an idea, also describe other ideas that are close but not quite the same. This will help people understand what the important points are that define your idea.
4. Ask Rhetorical Questions. Don’t make them too easy. Don’t make them too hard. Wait 6 seconds for an answer.