Do you want to know why Guy Kawasaki was made the head evangelist by Apple in the mid-1990s? Because Guy’s so smooth:
You should give your ten slides in twenty minutes. Sure, you have an hour time slot, but you’re using a Windows laptop, so it will take forty minutes to make it work with the projector.
Actually, the entire post is about Guy’s optimal PowerPoint presentation. (He sees a lot of them as a venture capitalist.) If you give presentations, it’s a worthwhile read.