If I hadn't lived in Los Angeles for a decade, I don't think I would have felt comfortable writing about it. It takes a long time to know this city, if knowing it is even possible, and I researched a lot before starting my novel a few years ago.
I was already a big fan of Carrie Fisher's Postcards From the Edge and Janet Fitch's White Oleander. I also read everything from Mildred Pierce to Sue Grafton mysteries to Joan Didion's Play it As it Lays to L.A. Noir anthologies. I drove around my own neighborhood, and neighborhoods I wanted to depict, taking mental snapshots and jotting down notes.
Since my main character is a recent transplant, however, I also had to keep in mind that she wouldn't know the city as well as a local would. I wanted her outsider-reactions to the quirks and oddities of L.A. to feel authentic, too.
At the moment, I'm reading Jamie Ford's terrific historical fiction novel, Hotel on the Corner of Bitter and Sweet -- which takes place in Seattle -- while on a trip to Seattle. It wasn't planned, but I love when that happens; when the feel and essence of a story seeps into your surroundings.