Modern cities a gradually filling with large glass and steel structures that provide wonderful opportunities for photographers to capture interesting reflections. Some buildings are faced with tinted or reflective glass featuring a metallic coating to reduce solar heating. The metallic coating produces a mirror effect and prevents those on the outside of the building from seeing inside. However, it also provides wonderful reflections of other nearby buildings.
Capturing detail is important when photographing modern buildings, so bright sunlight can work really well. Reflections are present under most lighting conditions. Early mornings, late afternoons and weekends are obviously good times to avoid the presence of people in images. Blue skies with white clouds make good reflections when seen against a background of regularly spaced windows. Find an interesting angle of view which places vertical and horizontal lines at an angle in the composition.
Photographs of modern building may be enhanced by including reflections, but the reflections themselves are often a more rewarding subject. Zoom in close enough that the overall form of the structure is lost and the images become more or less abstract, and try to incorporate reflected objects such as old buildings, church steeples or whatever is available. Buildings that feature several faces positioned at different angles also make good subjects. One face may be seen reflected in another, leading to reflections incorporating all sorts of confusing and interesting angles.
Another interesting feature of reflections from modern buildings is that each individual pane of glass may be set in a slightly different plane. Some panes may also bow slightly inwards or outwards. This produces a quite different effect in the reflections from adjacent panes, and hence a type of deregistered effect.