Well, the easiest way is to take the Tolkien tropes and poor them into guilds and districts:
Graceful, immortal, nature loving Elves
-> Garden district, a district with hanging gardens, Babylon style. Provides most of the food for the city. Besides food, the Elves also cultivate drugs and magic herbs here. The Elves themselves are obsessed with beauty, youth and keeping their district pure and clean of foreigners (basically any non-elf). Unlike in other worlds, the Elves are immortal but they do age, so they preform all kinds of rituals to combat their aging.
Subterranean, metalworking, hard-drinking Dwarves
-> Industrial district. Here the boilerworks of the city are found, as well as the smithies, weavers and breweries. The dwarves themselves are rough folks, fond of industry and beer. Ever so often a part of their district is trashed because a pub fight spiraled out of control, but the dwarves don't seem to mind. They're constantly at odds with the authorities for being rowdy law-breakers and with the elves for causing pollution. Dwarven Miners and Spelunkers maintain the sewer system and the undercity mines from their industrial district. Ever so often they run into something that should've remained sealed. As a result, and because of constant skirmishes between them and the elves, this district is reminiscent of a fortress. The dwarves police themselves and have no need for stinkin' human authorities.
Evil, aggressive, chaotic Orcs
-> The outer slums. Here you can find casinos, brothels and shady pubs, as well as the occasional black market at midnight. This district is run by ruthless men and fallen elves who use Orcs as their bodyguards and henchmen. Also expect to find cultists and temples to the dark powers here. If you need something from outside the city or you want to get someone killed, this is the place to look. The streets themselves are dominated by gangs of renegade Orcs, human thugs and Dwarves looking for a fight. Some elves come here for special rejuvation potions and rituals, because the contents and techniques employed are of highly illegal nature. Usually shunned by the authorities for being too dangerous, except for once every year when they have to clean up the mess left behind by a demon summoning ritual that got out of hand.
Courageous, greedy, powermongering Humans
-> The authorities themselves, as well as the official religious system. Corrupt to the bone, they'll gladly forget about your transgressions for the right price. Due to their fear of death and distrust of their servants, they're proficient necromancers. It's said that the official police force are just a front end and the real police force can be found in the mortuaries. There are a lot of departments: The department of industry, waterworks, agriculture et cetera, who're constantly at odds with each other and with themselves. Assassinations and even wars over things as petty as a new canal aren't unheard off.
Lowly, skulking, kleptomaniacal Kobolds
-> Street Urchins. Found everywhere, but especially in the merchant's district.
Powerful, wise, possibly insane Wizards
->University District. The wizards and artificers living here have a knack of breaking the laws, both of the city and of nature. Their district is larger than someone walking around it would expect, for example and it's utterly impossible to read the maps of this district. Vile fumes, towers of fire, ball lightning and blizzards can peacefully coexist in this district. If you need a potion, a golem or a new boiler you're likely to find one here.
Benevolent religious group that only seeks to bring peace
-> Medical District, lead by a religious order. Officially excommunicated by the religious authorities, they have taken up residence in the old temple district. They try to help where possible with outbreaks of diseases and the aftermaths of riots, as well as exorcising demons and undead whenever possible without attracting the ire of the authorities or cultists. Their cementary is an ever-growing liability and the knowledge about demons and the undead stored in their libraries make them a target for both the authorities, cultists and the mage guild. Much of their knowledge is also inherently dangerous and members of the Order always run a risk of becoming possessed.