In the comments, he also talkes about note taking. I wanted to say something about taking notes after the game; I had also heard something like that on Fear the Boot. I googled for the opposite of preparation and guessed that somebody must have used postparation. And indeed, somebody has:
Taking shorthand notes during the game, and making them readable after the game are mandatory for my games. Otherwise I’d forget. Since everything new happens at the gaming table, I can just add these little notes to our Campaign Wiki after the game. If the players have met ogres once or twice, the ogre page on the wiki may be very short:
It’s great. It works.
It’s not “prep” but it’s still a little bit of work. But since it comes after the fact it doesn’t railroad anybody.