God have mercy on your soul. I'm taking it as a 2L and dreading it.
I suggest focusing on any frameworks that the professor laid out in class. For example, as we learned commerce clause jurisprudence, the 3 major questions are 1) What is "commerce?" 2) What is "among the states?" 3) Does the 10th Amendment matter? They're broad questions, but by asking and answering them, you can address previous cases & rationales, then apply the facts from the exam scenario.