For my answer, the closest I can come to universal rules of etiquette are:
- Don't be a jerk. By which I think for nearly all tables means don't attack or belittle other players or aggressively argue with the DM and other players.
- Practice decent hygiene.
Not that these are not ever broken, but I think that while many of us have stories of these rules being broken, that these are usually told as horror stories and I've never seen anyone defending this behavior, beyond perhaps excusing it due to someone having a bad day or mental health issues.
Examples of etiquette that seem to be strongly enforced at some tables and not at all at other tables...
- Don't use someone else's dice without asking. I've met some players that simply will not let other people use their dice or at least certain dice. Always felt it was a little weird, but I do follow the general rule of etiquette of not grabbing other people's stuff without asking first.
- No electronics at the table. Differs table by table, but at some tables it is seen as a strong breach of etiquette to be looking at your phone during the game. I'm of a generation where I admit to a kneejerk negative reaction when people keep glancing at their phones during meetings, meals, or at games, but my current group is pretty laid back about it, we all have families and may have to interrupt the game so someone can take a call or respond to a text, but we try to keep it to minimum.
One rule of etiquette that I enforce at my table is no politics. I find that this is very much not the norm, but I also have noticed that the tables where this is tolerated and doesn't cause issue is because the group is very similar in their political and religious believes and the comments are generally quick asides. I ban it not just to avoid arguments. In my experience, political discussion can easily go into a long tangent that eats away at game time. Even when people are in agreement, it can lead to 20 minutes or more of discussion. I don't care what the topic is or what side someone is on an issue. I may be 100% in agreement with them. But I have one time a month I can run my game and I get enough politics in my life. I don't think it is too much to ask people to just shut up about politics for a few hours once a month. I'll not reinvite people to my game over this. Which is probably a bit harsh compared to the norm and can be a shock to new or guest players once they realize that I'm serious about it.
As a background to my answer, I'm American from the midwest (Twin Cities area, Minnesota). Started playing in the 80s. My childhood groups were mostly Caucasian and a few Asian mid-westerners. Apparently uncommon for that era, we had a lot of girls in our gaming groups. Maybe not 50/50, but there were always a couple girls at our table. Most of us were either standard 80s nerds or theater kids. Dropped out of the hobby for a couple decades and got back into TTRPGs in 2014/15. My main D&D group is all Caucasian, one woman and 3-6 men (3 who attend regularly and a few who drop in for a session when they can). A couple ex-military guys, some people in IT, someone that works at a prison, a furniture maker, a carpenter and another is a controls engineer.
I work outside of the US much of the year with an extremely diverse group of colleagues from many different countries, mostly from Europe and the Mideast. We play board games together but no TTRPGs. The party game Werewolf [not the WoD TTRPG] is the closest I've come to a role-paying game with them. Beyond that I've played in some Adventure's League games and have gone to Con of the North a few times, but I don't do a lot of gaming at conventions or game stores.
