The most important prerequisite is a good score on the LSAT. An undergraduate (bachelor's) degree is generally required, as well (some exceptions exist for VERY special, unique circumstances).

Vesper, in the U.S., you have to take the LSAT test, and I strongly encourage you to take an LSAT preparation course FIRST. Your LSAT score is tremendously important: http://en.wikipedia.org/wiki/LSAT Law schools also care about your college GPA (grade-point average) and the reputation of the college you went to. However, don't be discouraged if you went to a small college and want to go to a famous law school. It makes it harder to get in, but you can do it. It just means you need to write a great essay and have a good LSAT & GPA. In your essay, you might want to point out that coming from a small school means you will add some diversity to the incoming law school class. Diversity isn't just about ethnic origin; it's also about regional background, income class, and so on. Be sure to point out what makes you different; what makes you able to bring a different perspective to your classwork (and to your classmates). Each school is looking for different things in the students it chooses. They look at your classwork, volunteer work & life experiences you've had outside of class, and at your personal essay. Make the esagy a good one. Speak clearly and from the heart; that will get you further than just repeating formalized gobbledygook that the Admissions Office has seen ten thousand times before. You do not need to major in English, or political science, or "pre-law," or history. For instance, people who want to be patent attorneys often major in engineering. People who want to be medical malpractice attorneys might major in nursing or "pre-med" (or, as Antigone's friend did, biology). Some applicants might have a background in law enforcement or the military. What's most important to you is to try to guess at what kind of attorney you want to be, and then figure out five law schools that have a good reputation for that specialty. Write to each one or visit their website to find out what qualifications they demand.