Non-rule Rules in my Campaigns

Someone asked on Enworld about informal conventions and customs in people’s games that go beyond the mechanical rules of the game system, and it occurred to me that I actually have quite a lot of those. Might as well share the list here:

• My campaigns are set up to be about exploring the world, not the characters. Adventures are expeditions by the party, not personal stories. Players are free to drop in and out of the campaign without disrupting the campaign too much. As long as three players make it to the game, we play.
• When making characters for the campaign, there’s only two hard rules they have to follow: Every PC must want to go exploring dangerous places, and has to want to cooperate with the party for this. Antisocial loners who are reluctant to go on adventures are simply not viable for the campaign.
• Create characters with the assumption that they will probably die in some dark hole from an accident or getting stabbed by a nameless critter and that you might go through two, three, or even more characters before the campaign wraps up.
• Since PCs are replaceable and to some degree interchangeable, backstory is something that the players can create to help deciding on their characters’ personality and stats. It won’t normally be relevant in play.
• When players want to take an action against other PCs, (attacking PCs or messing with their possessions) the offending players have to openly state the actions their characters are contemplating. It is then up to the defending players alone to decide if the offending PC goes through with the action or not. If the defending players decide on on, then the offending players have to accept that their PCs decide not to do it.
• My role as GM of the campaign is to facilitate the game for the players. I try my best to provide a world that has places to explore and treasures and wonders to find, and villainous NPCs who are doing their villainous things which the players can choose to try to topple and drive out if they want to. I’ll describe what the PCs see, answer questions about the world, and try to make NPCs react plausibly to what the players are doing, given the resources and powers I’ve written up for them.
• As GM, I don’t have a stake what’s going to happen in the campaign. I describe the situation to the players, the players state what they want to do, we run that input through the mechanics of the game, and I interpret the output of the dice to describe the new situation. I just run the game computer, I don’t plot or conduct the adventures.
• Everyone can die. All NPCs and monsters have their stats fixed, and the game mechanics and dice decide which attacks and spells succeed and what effect they have. If the big bad dies in the first round or the party gets wiped, that’s the story that is playing out.
• I will always try my best to make anything that could potentially kill a PC visibly look like a real threat. I want players to always make a conscious choice to put their characters into mortal danger. It will never appear suddenly without warning.
• Retreat or surrender are almost always an option. (Though the players still need to work to pull it off.) Encounters are not dialed in to ensure the players can win.
• The requirements for progress on character advancement are objectively stated as standard mechanics of the game, or defined at the start of a quest. Progress points are gained when those requirements are met, in the specified amounts.
• Any die that falls off the table automatically counts as failure against the player’s favor.
• Only the GM can call for a roll. Players can not announce a roll.
• Every roll that will lead to an immediately visible result for the PCs is rolled in the open.
• For random events like Wandering Monster encounters or a rotten bridge collapsing, the roll is a single die with the probability of “1 in N”. The standing rule is “Something always happens on a 1”. What is going to happen on a 1 is specified before the roll is made. The die is rolled by a player. (Which makes it clear that what happens is not the GM’s personal preferred outcome.)