Kind of off topic - but I happened to be sitting next to Steve when he created a couple of those conference talks. He literally started preparing months before the talk. He would work on his wording over and over and over. Since I happened to be there, he would often try out his "lines" on me and ask me what I thought (I had to correct him a lot. He really wasn't technical all.) He practiced over and over. And for the diagrams he had good help from people who understood that simple diagrams are always better (avoid cognitive overload). And don't buy the book "Presentation Secrets of Steve Jobs" - I looked though it and that author has no clue about how those presentations were really created.