Black and white photography is a complete world on its own. Key aspect to consider for this type of photography is the decision to elaborate a B&W photography, as it can be a planned intention, or in other cases it will simply be opportunistic. When working with analogical photography or instant photography (Polaroid alike), the decision is made in the moment of the purchase of the specific B&W film required to take this photography type. While with digital photography there are different options to obtain a B&W photography, from specific predefined shooting settings to the result of the post-production.
The light type is probably one of the most important elements to consider when aiming to take B&W photographies. Hard light conditions will create sharp edges, high contrast, and very dark shadowed areas in contrast with other areas highly illuminated giving great visibility to the details and surfaces illuminated. Soft light conditions will allow to develop images in which there will be less contrast between black and whites, more harmonic and balanced images, softer and fuzzy edges as well as providing a smoother look from surfaces.
The subject and scene that is photographed play also a role to help you make a decision about when a photography should be shot in B&W. Portraits are commonly set in B&W, as the soft light used in this type of photography facilitates to create very smooth and pleasant photographies. On the other hand, spaces or scenes exposed to direct hard light conditions, can also call for B&W photographies, in which the intense contrast achieved from the light conditions will be magnified in B&W. This can be a great tool to elaborate more creative or abstract images, in which the balance and contrast between the whites and the absolute darkness can create strong emotional impact on the viewers.
I personally tend to use B&W photography for scenes or subjects that evoke older days and memories, impose authority or represent the pass of time. The one above is an example of this utilisation, in which B&W is also used as an element to provide a specific atmosphere in the image.