How to prepare your presentation from conception to rehearsal to handouts
“I’ve said it before here and here, and I’ll say it again. Your PowerPoint file is not your presentation; what you say before an audience is your presentation. (Exception: if it’s a self-running presentation at a kiosk, it’s your presentation, but then your slides need to be much more complete to be effective.)
Therefore, before or after you create your slides, you still need to write your presentation.
If you create your slides first and then your presentation, expect that you’ll find that the logic of your content will lead you to change (and improve) the organization of your slides.”