You have the Old Hollywood Glamour style that everyone recognizes: it is a concept that can perfectly cover the period from 1930s to the 1950s. Very elaborated hairstyles, usually involving curles and waves, grown up and sleek make-up, whose trademark is the red lips and to finish the look, sultry and long gowns with a sophisticated "Haute Couture" feel. You keep that as base and make it dark, much darker and more sexually conceptualized and you will get more or less what film noir is about. In order to understand what the whole thing is about, there are two key elements to know: 1st, the film noir concept (the aesthetic, themes or usual storylines) and, 2nd, the femme fatale, which, in my opinion, is the key element of this stories because is usually the main element that triggers all the problem and as a consequence, the fatal ending.
I have split this whole thing in two parts: part1 the concept, part2 the "femme fatale" issue. Enjoy! The below text was taken from this link: http://www.filmsite.org/filmnoir.html
Feel free to click on the link and read more on the original site.
Film Noir (literally 'black film') was coined by French film critics who noticed the trend of how 'dark', downbeat and black the looks and themes were of many American crime and detective films released in France to theatres following the war.
Classic film noir developed during and after World War II, taking advantage of the post-war ambience of anxiety, pessimism, and suspicion. It was a style of black and white American films that first evolved in the 1940s, became prominent in the post-war era, and lasted in a classic "Golden Age" period until about 1960. There were rarely happy or optimistic endings in noirs.
Very often, a film noir story was developed around a cynical, hard-hearted, disillusioned male character who encountered a beautiful but promiscuous, amoral, double-dealing and seductive femme fatale. She would use her feminine wiles and come-hither sexuality to manipulate him into becoming the fall guy - often following a murder. After a betrayal or double-cross, she was frequently destroyed as well, often at the cost of the hero's life.
The primary moods of classic film noir were melancholy, alienation, bleakness, disillusionment, disenchantment, pessimism, ambiguity, moral corruption, evil, guilt, desperation and paranoia.
Heroes (or anti-heroes), corrupt characters and villains included down-and-out, conflicted hard-boiled detectives or private eyes, cops, gangsters, government agents, a lone wolf, socio-paths or killers, crooks, war veterans, politicians, petty criminals, murderers, or just plain Joes. These protagonists were often morally-ambiguous low-lifes from the dark and gloomy underworld of violent crime and corruption. Distinctively, they were cynical, tarnished, obsessive (sexual or otherwise), brooding, menacing, sinister, sardonic, disillusioned, frightened and insecure loners (usually men), struggling to survive - and in the end, ultimately losing.
Storylines were often elliptical, non-linear and twisting. Narratives were frequently complex, maze-like and convoluted, and typically told with foreboding background music, flashbacks (or a series of flashbacks), witty, razor-sharp and acerbic dialogue, and/or reflective and confessional, first-person voice-over narration. Amnesia suffered by the protagonist was a common plot device, as was the downfall of an innocent Everyman who fell victim to temptation or was framed. Revelations regarding the hero were made to explain/justify the hero's own cynical perspective on life.
Film noir films (mostly shot in gloomy grays, blacks and whites) thematically showed the dark and inhumane side of human nature with cynicism and doomed love, and they emphasized the brutal, unhealthy, seamy, shadowy, dark and sadistic sides of the human experience. An oppressive atmosphere of menace, pessimism, anxiety, suspicion that anything can go wrong, dingy realism, futility, fatalism, defeat and entrapment were stylized characteristics of film noir. The protagonists in film noir were normally driven by their past or by human weakness to repeat former mistakes.
Film noir films were marked visually by expressionistic lighting, deep-focus or depth of field camera work, disorienting visual schemes, jarring editing or juxtaposition of elements, ominous shadows, skewed camera angles (usually vertical or diagonal rather than horizontal), circling cigarette smoke, existential sensibilities, and unbalanced or moody compositions. Settings were often interiors with low-key (or single-source) lighting, venetian-blinded windows and rooms, and dark, claustrophobic, gloomy appearances. Exteriors were often urban night scenes with deep shadows, wet asphalt, dark alleyways, rain-slicked or mean streets, flashing neon lights, and low key lighting. Story locations were often in murky and dark streets, dimly-lit and low-rent apartments and hotel rooms of big cities, or abandoned warehouses. [Often-times, war-time scarcities were the reason for the reduced budgets and shadowy, stark sets of B-pictures and film noirs.]
Some of the most prominent directors of film noir included Orson Welles, John Huston, Billy Wilder, Edgar Ulmer, Douglas Sirk, Robert Siodmak, Fritz Lang, Otto Preminger, Henry Hathaway and Howard Hawks.