Here's what I've heard (maybe 1Ls out there or Andrew can shed some light):
the exams aren't necessarily based on anything that the professor may have covered or taught. The professor has upwards of 100-200 of these things to read, so he's not looking for a long-winded essay. in this respect, apparently a quick outline with a few sentences on your reasoning will suffice for a good grade. Also, I'm under the impression that you can get away with not going to class at all and still acing the exams just by reviewing the commercial outline for the course, and possibly taking notes from it to take into the exam with you.
Coming from engineering, I'm not sure I will be able to adjust to this type of grading...
Ideally, you should be getting As if you know the material. However, you're grade really is your exam. And since I'm a terrible writer I don't think its that easy to pull off an A under timed pressure.