I’ve never had a session 0, but I hear they’re great. It seems good expectations about what kind of game you’re going to run before a player shows up to your tense political game carrying a sheet for Brawlnald MacDonald, the barbarian burger clown. At they’re best, they can give players a chance to get hyped about their characters and the adventure before things even get going.
This is just a nice way of conceptualizing the game you plan to run is nice, digestible terms. A few scales defining the tone and focus of the game, a diagram where you can mark it’s emphasis between the 3 pillars of play and the real quick and dirty details of the campaign – who, what and why.
I haven’t used this yet but I certainly plan to when I start aback up again, which is an inevitability. Here’s a link to a PDF, which should be easier if you’re printing.