Rule Zero - in-person or VTT: NO POLITICS
When I started my first campaign after getting back into TTRPGs with 5e, I started with two friends who I had played with during high school in the 80s. One is very conservative and one is very liberal. They remain good friends, so they can get along well despite vast political differences. But once they get started, they.just.can.not.stop. I've been embarrassed being with them in public places when they go at it. And the chance to discuss anything else goes out the window once they get going on politics. So I made it clear that any discussion of politics was not allowed in my home on game day. All new players have had to agree to the same rule and I am not shy in enforcing it.
I'm glad that in a very divided time that I have players from a wide spectrum of political and religious beliefs, and lifestyles, that can get together for 8-hours or more once a month and treat each other as humans.
PRE-COVID (In-person, at my home)
1. FOOD: Bring snacks to share. Occasionally we do full-meal potluck for lunch, when we do, everyone cooks something or at least buys a something pre-made other than a snack.
2. Alcohol: I'm the DM and it is my house and I'm the only one who ever drinks. Usually a beer or two.
3. Smoking: outside
4. Electronic devices: we use DnD Beyond, though some players perfer to work off the printed sheets. Our sessions are at least 8 hours. Occasionally an important call has to be taken. It really hasn't been an issue. What has been an issue is player who play games on their phones during the game. There is a zero tolerance rule for that. For non-DnD one-shots, I usually ban electronic devices at the table.
5. Be ready on your turn. Some flexibility is warranted but if you slow the game too much we just skip your turn and come back to you at the end of the round.
POST-COVID (VTT)
Of the in-person rules, only 5 really applies. I have no idea what other software may be running on player's computers. So long as they are ready and engaged, I suppose it doesn't matter. I guess I could say that for in person games, but having people's eyes constantly on their devices during an in-person game is more annoying.
I don't really have any additional rules for VTT games other than having a back up method to participate if your internet has issues. I use Google Hangouts that has dial-in numbers, so player can still participate by phone in a pinch. It only happened once and worked out okay.