What do I want when I buy a city off somebody? I want them to do work for me. Not necessarily work I couldn't have done myself, I just want them to have put in the hours to put a little love into things I myself was too busy with other things to do.
So, scoring your city supplement:
-You get one point for each thing described. An NPC, a building, an item, a unique local custom, a bar game, a legal system, etc. For example: you can say "there's a church" and you get a point.
Clarity at High Speed
-You lose that point if you tell me anything about it that could just as well have been randomized or made up on the spot by anybody with a brain, like: "the church doors are eleven feet high and made of oak."
I can make up generic details myself, I don't need professional game designers for that. More importantly, doing that clutters up the graphic design on the page when I'm in the middle of the game trying to figure out what's going on with your church. This may seem harsh, but the whole point of using someone else's setting is that you have to do less work and if I have to prep and highlight all over the page or rewrite it then it suddenly becomes more trouble than just writing my own thing.
-You lose a point if you explain the function of a thing when I already know what it does. Like if you say "the Cathedral of Chuckles is the center of the worship of the Great God Chuckles" you're wasting your space and my time.
Notice that from these rules the effect is: if you include a church and do nothing but give me generic details about it and describe what a church is, then you've actually lost a point and so you are better off leaving the church out entirely if that's all you're going to do.
-You gain 0 points for putting the thing on a map or otherwise locating it, unless where it's located has some especially distinctive effect on the game or setting, in which case it gets you one point. Telling me the crypt is in the northeast quadrant of the city doesn't get you a point unless that means the graveyard is built on top of the all-girl juggling school. Again, if you're giving me a detail it needs to be a detail that couldn't just as well have been randomized.
-0 points if there's a map that's keyed with only numbers or letters referring to paragraphs spread out across the supplement. Five points if it's keyed with the names of places and/or some sort of distinctive shape telling you what something is just by looking at it. Twenty points if the spread with the map manages to both locate a place and encapsulate most of the important things I need to know about each location.
-You gain a point for adding a descriptive detail that affects the style of the thing. That is: creates some sort of shift in the idea of the thing by its mere presence. For example: telling me the church is shaped like perfect sphere, or an antler, or is made entirely of leather, or is a monolithic grey streaked with long dark stains from centuries of rust and rain. Ideally, You get this point even if it I don't like it--like you say the church is made of burlap and magic lutes.
Adventure Fuel And Completeness
-You gain points for adding distinctive features to things that create playable depth --information, "adventure seeds", mini-challenges--to a thing you've created, according to the following scheme:
-One point for a detail that basically says "There's an adventure you could go on outside the setting" (no matter how lame). i.e. "It is rumored that the priest has a map to the location of a sunken wreck full of treasure." (Assuming the description of the actual wreck and map are not provided in your setting.)
-One point if the adventure being pointed to isn't lame.
-Two points for a detail that points the PCs towards an adventure outside the setting and implies that some person or institution in the setting will be pleased, displeased or in some way affected by completion of the task, and if that person or institution has any identifiable and persisitent personality or role in the setting. i.e. "It is rumored that the priest carries the map because he hopes, one day, to recover the dog collar belonging to his dead puppy, Randolph, who died on that voyage."
-Three points for a detail that could send the PCs out of the setting but which will, if they succeed or fail, create a substantial change in the setting. i.e. "Legend has it that returning the collar to Charneldyne will cause all the madmen in the city to become sane."
-Four points if it sends the PCs out of the setting but also requires or implies that in order to complete the task they must do something substantive within the setting. "The ruined galleon is a mile beneath the waves. It is said there are only a handful of devices and substances that allow one to reach such depths, and a scant few in the city who know how to use them--and they all have been imprisoned by the Baron for either necromancy, lechery, or fraud."
-Five points if the task can be performed entirely within the setting. "The wreck is actually located deep beneath the surface of the Baron's moat."
(Or, to put it another way, the easier you make it for me to run the city just like a dungeon, the happier I am.)
(I'm all for "leavng space for the DM to invent things" but I don't need you to provide that--I know I can create space wherever I want. I'm subcontracting you.)
-Six points if a detail could be of general use to many, most, or all of the PCs activities within the setting. "The priest, like all the clergy in the city, is unknowingly subject to a ancient curse from the Sea Gog, Nykkto, whereby his intimates are doomed to die by drowning."
Five points for each part of the basic premise of the city that is actually interesting. i.e. "The City of Charneldyne is a bustling metropolis at the heart of the orcish empire" would get 0 points, whereas ""The City of Charneldyne is a bustling metropolis at the heart of the orcish empire and is built entirely from the bones of slain foes" will get 5 points.
Twenty points if the setting as a whole is actually interesting. Like Viriconium.
Neither gain nor lose points either way if it's just basically a medieval place.
You lose twenty points if it goes out of its way to be uninteresting, like Stamford, Connecticut.
Divide the number of points by the cost in U.S dollars of the setting.