Below are the policies we're using for the game we're prepping. There are a couple that are specific to the setting, but I think that most of them are relevant to most games. We've split the difference between just "don't be a jerk" and listing specifics.
Rule One
Our first and most important rule is "Don't be an asshole." Don't harass your fellow players, don't be a creep, don't metagame, don't share IC info/resources between alts, don't power pose... it all comes under the heading of Rule One.
Non-Consent
[Game Name] is a non-consent game. While we encourage players to work together to arrange for a mutually-agreeable solution, in-character actions have consequences, which cannot be avoided. If the player would like to avoid roleplaying out the consequences, they can always request a Fade to Black, and that request will be granted without question or delay, but the character will not avoid the IC consequences.
Alts
All players may have up to three PCs. They should generally not have the same role and should never interact ICly.
Player-Run Plots
We encourage them. All we ask is that you run the general idea past a Staffer before scheduling it. If it's a combat event and you need help setting up combat, just ask. If you want to run something off the cuff? Do it. We just ask that you don't destroy the Guinevere, kill a great dragon, or shatter a nation. Bar brawls, shady info exchanges, spy extractions, and dogfights with air pirates or wyverns/wyvernettes are all totally fair game.
Magical Artifacts
We're great with players coming up with magical McGuffins, and even doing it on the fly. They can even be potent and powerful within the plot itself. But all major artifacts will end up in some giant government warehouse ala Indiana Jones or Warehouse 13 (but might come back up later). Minor artifacts may be approved as plot rewards on a case-by-case basis, but they will never be something that provides a direct game bonus, they will only ever be things that provide flavor to RP. Things that provide bonuses count as major artifacts and will end up in a warehouse somewhere (stupid governments).
Language
We're an R-rated game (although we aim for PG-13 on channels), and we use the Translation Convention: 1930s curse words don't have the same impact on modern readers, so feel free to use the curse words that come naturally to you (although we do ask that you avoid modern cultural references ICly, of course).
OOC Discrimination & Harassment
We won't stand for it. Period. If someone harasses you, please let us know immediately -- there's a good chance they're doing it to someone else too, and we absolutely want to know. Depending on the circumstances, we will usually give one warning, but that's it. Ares has wonderful reporting tools so we don't have to worry about he-said/she-said issues (check out the channel/report and page/report commands and the ability to forward any harassing mails).
IC Discrimination
We've specifically designed our setting with the Great Upheaval to remove issues of discrimination against women, people of color, and LGBTQ+ people. We've also bumped off Hitler and replaced the Nazis with the Drachenordnung to shift the focus of fascism in Germany away from Jewish people. So just don't do it. We're great with characters who just plain don't like one another, but this is not the game to live out your dreams of "historical" misogyny, racism, homophobia, or other -isms.
Privacy
Staff will never read pages, mails, or anything like that unless they are sent to us via the built-in reporting systems as part of a complaint about inappropriate behavior. Staff will never watch private scenes unless we are explicitly invited to do so (and all participants approve). Please be aware that things said on channels are retained in the backscroll for some time and may be visible to people not logged in when the comment is made.