Rather than banning content which just makes players find a work around. I prefer something like a CoC or w/e.
1. Don't be a douchbag, or professionalism.
You can be that roleplaying tree hugging hippy and Bob can be the dice freak that RPs using terms like "teabag thar noobs!" for all I care. Make some damn effort to get along, don't grab Sue's tits as a 'joke', don't bite someone's hand for reaching for the chips. I mean, we're here to have fun pretending to be heroes and the world really does center on us. Not to play your therapist and hear about how you beat animals before going to sleep.
2. Don't be a douchbag, or gentleman's a agreement.
Being cool is awesome, but this is a team effort. There is no 'I' in team or 'U' so hardy hardy har share the spot light. Means if someone wants to be a fire focused Sorcerer, don't roll up a Wizard that brags about his Fire spells being better. Don't fall into the escalation trap, if Bob deals morei n combat from you setting up his SA don't go uber charger so I'm forced to throw spellcasters at you.
3. No surprises.
Me 'oking' your sheet has little to do with me sitting down and adding up your ability scores or checking the exact wording of your totally 'legal' feat you copied from a book I forgot to download. I'm looking at things like concept, focus, and traits as to better handle encounters. Finding up "I Win" was you're 3rd level feat and using it means you turn off the lights and attack fifteen times in a row is a surprise I don't want. It's not me vs you unless I'm giggling manically, so play nice with the DM too.
4. I hate commercials.
Kind of 2 meets 3 becomes 4 but aimed at everything. Don't become a walking advertisement trying to teach everyone to play a Truenamer or w/e class you think everyone should place. If Bob likes the Rogue, let him play the Rogue. If Sue wants to play a Barbarian who hates your Bard, don't sit there telling her a Cleric is better of why magic is better than mundanes in an attempt to convert them. Nobody likes Jenova's witnesses.
5. When in doubt, ask me.
I like intent, I like a world where NPCs can afford to live and don't craft gold to make gold, and choking on water doesn't heal you. You want a silly illogical game, I need alcohol. Otherwise try being reasonable, ask before your horrible interpretation causes problems. And if you disagree with me, don't bog down the game, just bring it up later.