Session 0 is the pregame of an RPG, falling somewhere between recruiting players and beginning the campaign. Its usefulness as a tool cannot be understated. Even among friends (vs acquaintances or strangers) there are a few key points I feel necessary to discuss between DM and players, even in groups that have gamed together in the past, because new things can - and arguably should - always be tried.
Among known people, I don't know that the Consent in Gaming checklist is needed, but I would have it ready if gaming with utter strangers, such as when putting together a new group. Arguably, even among friends and family, it is useful - we don't know our friends and family half as well as we'd like to think.
Regardless of game, I firmly believe that addressing the following topics should cover most issues before they come up.
A good Session Zero helps prevent this.
-----
1. Game expectations. My default expectation is that we're here to explore dungeons, not characters, but I know not every player uses that default. This topic also covers setting/genre and if the goal is to play through a published Adventure Path or WotC hardback - both of which are railroad stories that anticipate PCs/players running through the steps or a more sandbox-style. Also addressed is what the game is NOT about. A partial method is to use step 1 of the Gygax 75 Challenge (some examples laid out here) and show pictures/movies/songs that inspire the setting. Hammering out each player's and the DM's expectations early should allow for a better game for all.
2. Rules and major houserules. Especially those houserules that may impact race/class choices. This is a fine time to discuss metagaming, specifically your definition of metagaming. Houserules may incorporate some or all of the other topics on this list, as well as anything else. DMs should have enough printed copies to go around, or at least share the document digitally.
3. PC creation. Which rulebooks are players allowed to pull from, plus any other bits and pieces, such as necessity of backgrounds and how stats are generated. Ask if PCs already know one another and perhaps they should. I'm in the camp that Session 0 is also when PCs are created. Not only does creating PCs together facilitate shared backgrounds, it also allows for players to possibly fill the various party roles that make up successful adventuring bands.
4. Plot armor for PCs. DMs need to be open about whether or not PCs are going to die, as well as the likelihood of PC death. If you're going to go all deus ex machina in your game, be up front about it. This is a fine time to address how replacement PCs will be brought into the game (I am not above having the new PC be a prisoner in the next room), particularly at which level and with how much starting gear.
5. Dice rolling. This covers rolling combat dice in front of players or behind a screen, what happens when a die hits the floor, and types of dice allowed (my personal rule is if I cannot read it upside down across the table, it cannot be used - save your art dice for another game!). If online, which dicebot you're using and what else that bot does (use Avrae because it also has an insult generator!).
6. Scheduling. Not just when you'll play (hopefully more than once a month), but what happens if someone cannot make it and the agreed-upon etiquette of WHEN the group is notified of an impending absence. The reality is that people miss sessions, be it for work or family (or other reasons). Not having a plan for absences can lead to frustration for all. Have a plan in writing when multiple people are absent - cancel the session or just play a different game for those folks? Or carry on? Related to this is what happens if a player's schedule changes and they can no longer play at all.
7. Puzzles. Some players love them, others hate them. Address if puzzles in this game are aimed at the PLAYERS to solve or can be solved by throwing enough dice at them and calling it PC-solved puzzles. This is probably a good time to discuss how finding and opening/disarming secret doors and traps will be accomplished in game - be it player description of PC actions, flavorless dice rolls, or some combination of the two.
8. PvP. I'm not a fan of players openly competing against one another, but some are. Regardless, it needs to be covered and should include using Charisma-based skills against one another, as well as all the other nonsense implied by 'its what my character would do.' If nothing else, use this section to remind players that it is 100% their responsibility to find reasons for their PCs to adventure with the other PCs. In a cooperative adventure game.
9. Table and house etiquette. Even if the game is in a store instead of a personal home, there are social rules to be followed, like smoke outside, don't feed the dog table scraps, I'm deathly allergic to shellfish, don't show up drunk or stoned, keep cell phones away, etc. A big piece of etiquette involves inviting friends to the game without letting the DM and host know.
10. XP or Milestone leveling. If XP, provide a solid list of what does and what does not garner XP.
11. Contact Information. Trade cell numbers, invite everyone to a private Discord server, provide a link to shared files or a blog. Just have a way to send reminders about game night, if nothing else. I'm a fan of Discord, though, so that folks can handle admin and individual tasks without wasting table time at it.
12. Safety Tools. In addition to the Consent in Gaming checklist in the opening paragraphs of the post, are a variety of tools designed to allow everyone at the table to enjoy themselves: X-Cards, Lines and Veils, Stars and Wishes, and Thorns and Roses. Golden Lasso Games describes each of these better than I could, so go read that post.
-----
Twelve points of consideration to discuss before a game actually begins. To be honest, Session Zero is everyone's chance to decide if that particular game is, in fact, for them.
And it may not be.
And that is okay.
There are other games and other tables, even with the same people.
Will addressing all of these 12 points make games go better? Maybe. Probably. Hopefully.
Will ignoring some or all of these to just jump right into the game cause issues down the line?
Yes. Unequivocally.
-----
What is this list missing? What should this list not include? Take advantage of the comments to tell me.
11/2/23 EDIT: Necropraxis wrote up 20 questions about game mechanics that are worth discussing in session 0.
