We have some player-enforced guidlines for CvC that get you in toruble with other players for not following, and some DM-enforced rules that can get you in trouble with the team if not adhered to:
1. No looting of items except for consumables/replaceables: A weapon, a helm or a magical wand are examples of things that can't be looted under any circumstances. Things that can be looted include but are not limited to magical potions, healing kits, ammunition, crafting components, gems and scrolls.DM enforced:
2. Withdrawal upon defeat: If you are defeated in CvC in enemy lands you must leave the area and not come back until twenty four real time hours have passed. The only exception is if you must retrieve your gear after the incident that caused your death in the first case, in that circumstance you may come back, claim your equipment and leave as soon as possible. If you go back to enemy lands before the 24h period has passed you won't be protected by the agreement regarding looting. A example of this would be some Llolth drow kicking you out of the Drow city - don't go back there for 24 hours.
3. Some spells and tactics are severely frowned upon, such as spamming Timestops to cast offensive spells, or using Hide In Plain Sight regularly. Using such 'cheesy' tactics will often invite other players to do the same to you.
4. No Bigby's Forceful Hand: This is the only spell that at this time of writing has been considered "broken" for CvC purposes due to the difficulty to resist its effects. Virtually nobody can succeed in the STR check required to avoid it.
5. Set your enemies to dislike: This is always the responsibility of the attacker and can be done as soon as right after logging in or as late as a split second before the actual attack but the bottom line is that it must be done.
5. Don't assault a city unless under DM supervision. Without a DM to put in realistic resistance, you'd be taking advantage of the NPCs' AI to make the attack easier than it should be. This applies to any sort of attack or criminal action, any applies to the Demon Temple, Mirtho Rest, Nagritch, Tel, etc.
6. No spies in the private boards of an opposing organization. A character can only spy in such a way if the DM sponsor of the spied guild knows about it. Further, all information spied must pass through this DM.