While colour photography allows the photographer to show a viewer all aspects of a given scene, that does not mean it is the best way to display the scene. Black and white images show contrast and light in a different way, which is a useful tool if the light itself is what the photographer wishes to convey to the viewer. Why would a photographer want to do that? Simply put, sometimes the quality of the light in a scene exceeds the interest of the scene itself. Not that a black and white conversion makes a bad image good! While interesting light can be transmitted in colour photography, there are times where the colours in an image are a distraction.
Black and white photography also transmits a different feeling to the image viewer, which is another powerful tool. How can a photographer use a black and white image transmit the intended message? One of the most important aspect of the process is choosing how to process the intended image.
In camera settings? Nothing unusual in terms of shooting settings. I generally use the monochrome picture control, while still shooting RAW, so that I can see what type of image is possible. Shooting in RAW means that I still get a colour image, should I so choose to use an image that way. In post I make basic RAW edits in Aperture and then move then make the black and white conversion in Silver Efex Pro 2. I like using Silver Efex because it has numerous different presets, and film emulation tools.