When I was studying graphic design many years ago the life drawing teacher would often give us an exercise based on perspective and object construction. The idea was to see the through the object, imagine it barely opaque so that you could draw it accurately with the help of perspective lines and such. The results were usually very accurate and, I would say, uninteresting. They left no room for mistakes or slight differences that make a drawing appealing. I do use some of those methods occasionally, but most of the time I like to just go with the flow, throw out all those rules and see what happens.