Step1
Read a book or two dedicated to the genre. A number of excellent books have been written on the subject, particularly the works of authors Alain Silver and James Ursini, which can provide an excellent overview.
Step2
Rent a number of noir movies. Titles such as "Double Indemnity," "The Big Sleep," "The Maltese Falcon," "Mildred Pierce," "Out of the Past," "The Big Heat," "The Asphalt Jungle," and "Touch of Evil" make excellent starting points, and most are available on video or DVD.
Step3
Watch the films carefully one by one.
Step4
Pay attention to the look of each film. Try to view each scene the way you would a still painting, observing how the different elements are arranged and the way they interrelate to each other.
Step5
Look for the way light and shadows are used. Noir movies emphasizes a strong contrast between black and white, dividing the world up between them. Look for things like street lamps reflecting off of puddles of water, Venetian blinds throwing bands of shadow across the scene and faces either render in a harsh, unyielding white, or hidden by the brim of a fedora hat and the like. In particular, notice how much of the film takes place at night.
Step6
Notice how the movies portray cities and urban settings. Noir often portrays cities as havens for criminals and the corrupt, tempting weak souls with promises and delivering nothing in return. Look for film to show a sense of corruption and decay: seamy back alleys, dirty underground clubs, and the like. In particular, watch for the way the surroundings seem confining and oppressive: the buildings looming over characters, for example, or the streets appearing maze-like and impenetrable.
Step7
Watch how the visual elements in the previous steps reflects the story and the characters involved. Noir often involves characters who succumb to their dark urges and pay the price for it. The principle figures often want something that they can’t normally have--a beautiful woman, a lot of money, or the like—and end up doing terrible things to get them. Their misdeeds always come back to haunt them, no matter how hard they try to escape. Observe how that overt storytelling ideas are emphasized by the way the film looks, and the visual choices the director makes.
Step8
Compare the main character in noir movies to those of other genres: westerns, for example, or romantic comedies. Notice how the “heroes” of noir films often engage in criminal behavior, or give in to their weaknesses so easily, while the main character in other movies are strong, dependable, and always come through in the end. And yet we are often asked to sympathize with noir characters and understand why they behave as they do, the same way we’re asked to sympathize with John Wayne or Errol Flynn in their movies.
Step9
Watch movies that came after the “classic” noir period of the 1940s and 1950s to see how they influenced subsequent filmmakers. “Neo-noir” movies like "Chinatown" and "L.A. Confidential" reflect the same themes and ideas, but you can also find strong noir elements in entirely different genres: science fiction films like "Blade Runner" and "The Matrix," for instance, or comedies like The "Big Lebowski."