hotels with a neon sign blinking through the window

Film noir is...

(1) A French term meaning "black film," or film of the night, inspired by the Series Noir, a line of cheap paperbacks that translated hard-boiled American crime authors and found a popular audience in France.
(2) A movie which at no times misleads you into thinking there is going to be a happy ending.
(3) Locations that reek of the night, of shadows, of alleys, of the back doors of fancy places, of apartment buildings with a high turnover rate, of taxi drivers and bartenders who have seen it all.
(4) Cigarettes. Everybody in film noir is always smoking, as if to say, "On top if everything else, I'e been assigned to get through three packs today." The best smoking movie of all time is Out of the Past, in which Robert Mitchum and Kirk Douglas smoke furiously at each other. At one point Mitchum enters a room, Douglas extends a pack and says, "Cigarette?" and Mitchum, holding up his hand, says, "Smoking."
(5) Women who would just as soon kill you as love you, and vice versa.
(6) For women: low necklines, floppy hats, mascara, lipstick, dressing rooms, boudoirs, calling the doorman by his first name, high heels, red dresses, elbow-length gloves, mixing drinks, having gangsters as boyfriends, having soft spots for alcoholic private eyes, wanting a lot of someone else's women, sprawling dead on the floor with every limb meticulously arranged and every hair in place.
(7) For men: fedoras, suits and ties, shabby residential hotels with a neon sign blinking through the window, buying yourself a drink out of the office bottle, cars with running boards, all-night diners, protecting kids who shouldn't be playing with the big guys, being on first-name terms with homicide cops, knowing a lot of people whose descriptions end in ies, such as bookies, newsies, junkies, alkies, jockeys, and cabbies.
(8) Movies either shot in black and white or feeling like they were.
(9) Relationships in which love is the only final flop card in the poker game of death.
(10) The most American film genre, because no society could have created a world so filled with doom, fate, fear, and betrayal, unless it were essentially naive and optimistic.

- Roger Ebert, "A Guide to Film Noir Genre"