The examiner is looking not only for substantive knowledge of the topic, but how to answer the question as well. The abilities to write well, fluently, and under time constraints are essential in order to pass a law school exam.
So, studying for law school exams requires not only mastery of the material in the particular class, but the ability to "show what you know" by writing answers to essay questions that spot the relevant issues, state the applicable rules of law, and present cogent analyses of the various issues raised by the particular question. Remember "IRAC:” issue, rule, analysis, conclusion.
The best way to study for a law school exam is to synthesize all the material learned in the classroom. Go over the notes taken in class, review the chapters in the hornbooks and casebooks used in that class, and review any commercial outlines that cover the particular topic. Take all those materials and put them into an outline, in whatever format works best, that then is the basis for studying. Modify and annotate that outline during studying for the exam.
Law school exams are usually given under strict time limits. Spotting the issues is critical to a successful answer. If possible, get copies of previous exams or even bar exams on the subject, and then practice writing essays. Practice, practice, practice. It is not just a matter of knowing the material, but knowing how to spot the issues and then write answers that see the issues, frame the applicable rules, and set forth an analysis, applying the facts in the questions to the issues and the rules. The best way to do that is to write as many essay questions as possible. A successful law exam answer comes to a conclusion; the correctness of the conclusion does not matter as much as the analysis that shows the professor an understanding of the issues.
The same holds true for studying for multiple-choice law school exams. Get copies of previous multi-state exams and practice answering them. Studying for multiple choice exams requires not only mastery of the material, but the ability to tease out the differences between more than one answer that appears to be right.
Studying for law school exams is not something that can be saved for a cramming session the night before the exam. Both time and effort are critical to success.