Your right, it is a bit subjective. I remember doing the same thing. The trick, in my opinion, is that every question has certain main issues, would should be the focus of your answer. Then each question has a number of small issues that go along with it. You can never predict what will turn a professors attention, so writing blue book after blue book may be necessary, but organize it with focus on the major issues an addressing the smaller one later, but emphasize the major one throughout. This advice may not what your looking for, but it worked for me.