City campaigns in a peanutshell:
You need a list of standard city characters: the ruler, body of rulers, head of church, head of state militia, and institution heads like a librarian, arena master, or top wizard.
Throw in another handful of interesting people, both in power and without power, like criminals, entertainers, soldiers, and crafts/guildsmen. (Interesting people need interesting places - so be sure to think about the top 3 or 4 places your PCs will want to go. Inns, blacksmiths, and breweries!)
Each of these people has motivations that cooperate and conflict with most of the others. Pick out a few interesting ones for potential plot points.
Give your city some interesting scenery: like a titanic tower in the middle, or trees instead of fireplaces.
Now wind up all your pieces and watch them in your head. Write down ideas.
My dwarves (hill dwarves, anyway) are heavy drinkers because they're all poor and pummeled by their theocracy. They organize in clans because the state won't let them form other organizations. And they don't actually live underground, but they got that reputation because they're excellent miners and some of their aristocrats moved into exhausted mines.
-Heinrich smiles. Cynthia smiles. Hermit attacks!