Really the only rule is having characters or elements that are completely absurd, such as a world nuke or some character that instantly mind controls others or something crazy, aren't allowed, and if people try having them, we can pretty much elect to ignore or eject them from the rp through our own means.
While my characters are scattered all over the place, since I'm about the only one who control multiple locations, most of the characters of the other roleplayers are at a location known as the Base. The base is south of a crater where a complex used to exist before it blew up, south of Vesuva. The Base is also south west of Zayin, while it is south east of Codspeace. East of the Base is the Ocean Base. Due to the nature of the revival, and me being the original creator of Vesuva, Zayin, and Codspeace, I currently control the majority of these locations, as well as most of the north considering the former Novaya and the Plagued Wastelands. So basically I have the north of the base.
That being said, if you wanted to make a location, make it somewhere south, please, to avoid conflicting with all of the locations already existing north of the Base.
Either ways, see you, it's 12 AM for me, 0 in military time, so Imma have to get off soon.