First, ask yourself if you can truly make objective evaluations of yourself (past experience is useful for this)
Do you have an excellent attention to detail? Are you really good at figuring out analogies? Metaphors? When you argue with people, could you use the exact same facts in different ways? Can you succinctly express nuanced ideas? Do you have an intuitive sense of what sort of expectations people create in each other through their conduct? Can you type fast? Can you make arguments despite personal aversions to your beliefs?
These are some basic skills that could really help on any law school exam. Because a law school exam involves:
1. Reading the set of facts: usually a story w/ tons of potential legal issues. They tend not to be much longer than a page or so, but they contain a lot of information that could usually both hinder and help both (or more) sides of any particular issue. Your facts are your ingredients, the more you can do with them, the more options you have in writing your answer. The more options you have, the more detailed your answer could be, and thus get more points...
2. Spotting the issues: This requires a degree of intuition. This involves remembering the rules, and sometimes the general themes and principles behind the rules. Could the facts fit into the categories envisaged by the rule? If so you spotted an issue. There are ways to practice this though. For example, in a crim law exam, if there are ever two or more suspects then you probably have to mention conspiracy as a possible issue... read enough past exams and answers and you'll start seeing the patterns that profs use.
3. Application: Once you've spotted the issue you'll explain which facts support one categorization over another. (probably 70+% of what your answer will consist of)
4. Writing the answer - Organization and preparation are key here... Do you know what your professor expects on an exam? Are you disciplined enough to move on to the next questions before finishing, if you are running out of time. Succinct writing, w/ headings that facilitate the professor awarding you points is best. (profs give points for you spotting the issue, and for the different ways you apply it... some have checklists, others have gut feelings... give them what they want, but make it easy for them... profs are lazy and not as smart as they think they are.)