Apologies if it's been posted recently but this story from last year people might find interesting again:
"Next week Steve Jobs of Apple will grab media attention with another simple-looking stage show. Mike Evangelist tells the insider secrets of his gruelling preparation"
http://technology.guardian.co.uk/weekly/story/0,16376,1677772,00.html
A sample quote:
"My first experience of this preparation came in the runup to the Macworld Expo keynote of January 2001, which was to include new Macs able to burn DVDs - then an amazing capability. Steve wanted to show off the new software, iDVD, that could do it. As I was the product manager for Apple's DVD software, I had to organise everything that Steve would need.
The team and I spent hundreds of hours preparing for a segment that lasted about five minutes. Several weeks earlier Steve summoned me to demo the software, and highlight what I thought were its most interesting aspects. Of course he already knew most of this, but the process was still useful. He used the key points from these demos to mould his overall presentation and decide how much time each product would get."