4. Integrate your descriptions with your story.
No one wants a big block of text describing the socio-political background of a city unless it has some relevance to the plot at hand. Descriptions are important, maybe even the most important, but they have to serve the story.
Remember -- quirks are good, but they're better if they fit within your story arc and serve to give the reader information about the characters.
Consider this example from GONE GIRL by Gillian Flynn.
“Our bar is a corner bar with a haphazard, patchwork aesthetic. Its best feature is a massive Victorian backbar, dragon heads and angel faces emerging from the oak—an extravagant work of wood in these shitty plastic days. The remainder of the bar is, in fact, shitty, a showcase of the shabbiest design offerings of every decade: an Eisenhower-era linoleum floor, the edges turned up like burnt toast; dubious wood-paneled walls straight from a ‘70s home-porn video; halogen floor lamps, an accidental tribute to my 1990s dorm room. The ultimate effect is strangely homey—it looks less like a bar than someone’s benignly neglected fixer-upper. And jovial: We share a parking lot with the local bowling alley, and when our door swings wide, the clatter of strikes applauds the customer’s entrance.”
Why does the description work? First, it addresses characterization. It tells us that our narrator (Nick Dunne, in this case) is bitter and cynical ("shitty plastic days") but also able to look on the bright side (the bowling alley is next door).
It fits within the story arc. It tell us that the owners of the bar cannot afford to fix it up and it subtly implies that they may not know what they're doing when it comes to running a business. It also arrives at the right time in the story--Nick has just explained that he lost his job as a writer, so he came home and opened a business with his sister.
Remember: If a description doesn't arrive at the right place in the story, it doesn't matter how good it is. It's just a paragraph in a brochure.