Well I am studying architecture, so drawing buildings is kind of part of my course. Studying architecture gives you a unique way of looking at a building, and being a designer means you pick out certain details.
Of the above drawings, some of them a very calculated and careful, some are drawn from photos, and some are original designs. But I really think that the msot important skill in drawing is the ability to setup a drawing carefully, but loosely, and build detail with an eye for composition. A good way to start, is once you have drawn the edges lightly, start shading planes according to their angle. Use horizontal lines for flat surfaces, and vertical lines for vertical surfaces. You get a clear sense of composition as you go.