If you are looking for this, going out in the morning or afternoon when the sun is at a low angle usually works best for high contrast black and whites.
Long shadows caused by the sun or light source coming in from an angle will elongate shadows and add them as ‘characters' to a scene. If you are looking for this, going out in the morning or afternoon when the sun is at a low angle usually works best for high contrast black and whites.  In urban areas this does not necessarily mean sunrise or sunset as the sun may be too low to make it over buildings and other structures.  Light during this time tends to be too diffused to make crisp shadows.  I prefer winter light for these types of images as the sun tends to stay low all day, even around midday, which is often the only time I get to hit the streets (Bonus tip: forego the sandwich and use your lunch hour to shoot!).