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 <b>postparation</b>. And indeed, somebody has:
Pre-paration is what we do before we start a job. Post-paration is what we do after we do the job. Completing all the postparation immediately after the job is what generates the feeling of well deserved relaxation. 
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:
The hills between Dangerous Jungle and Great Roaring Jungle seems to be infested with these giants. Then again, their minds seem to be weak. They seem to have a fascination with skulls. 
It’s great. It works.
It’s not “prep” but it’s still a little bit of work. But since it comes <b>after the fact</b> it doesn’t railroad anybody.