Below are some essential elements for writing urban fantasy fiction:

1. The setting should always be one of the main characters, and it should be an urban environment.
2. Urban fantasy stories incorporate fantastical elements and supernatural creatures.
3. Urban fantasy often has a dark noir feel, and it may involve mysteries and crime-solving, combat, romantic sub-plots, derelict settings, fantastical characters, and paranormal characters.
4. Magic is an essential element of every fantasy novel, including urban fantasy.
5. Characters should have unique voices and be well-developed, and there can be antiheroes that readers will love.

It’s important to note that while these elements are common in urban fantasy novels, they are not strict rules. Writers can subvert these elements and come up with something new. The most important thing is to create a compelling story that engages readers.