This one is from Jim Lee, one of my favorite comic artists and panelists. If you looked at the Batman sketch from Comic-Con the other day, you might have seen it. An audience member asked him about perspective cityscapes and he quickly drew radiated lines for 1 point perspective that went from narrow to wider gaps. He indicated this was a quick way to estimate perspective. This works well once you have studied perspective and done enough drawing to recognize when something looks out of place. You can do this quickly and lay in your buildings, and pull back the drawing to look at what needs correction. Also doing it by hand gives a more realistic feel. Using a straight edge gives the drawing a more diagram like sensibility.