The LSAT is an intelligence test that can be beat. Meaning practice and learning a methodology to answering the various types of questions can vastly improve on one’s “natural” score.
Regarding yeshiva training and law school, I think both akuperma and PBA are right. Many of the skills needed in Gemara are not needed in law school. However the ability to read very carefully and be medayek is quite useful (even more so in the actual practice of law)as is the ability halt kup with a cheshbon and the ability to reason by analogy. Furthermore, one’s ability in discerning and explaining lomdus can go the extra mile in impressing a Professor on an exam.
But probably the most important thing you can do before goin to law school is take a writing class and typing class (or use books/programs and teach yourself). Most law school grades are based entirely on your exams in which you will be trying to tackle as many points as possible within a strict time restraints. The Professor needs to understand what you mean and understand it easily (they are grading lots of legnthy exams and are not going take the time to read what you wrote twice).