If you know early on that you want to go to law school, keep that in mind as you choose your undergraduate courses. Many schools don't offer a dedicated pre-law program, and most law schools don't require one. Even more, the American Bar Association (ABA) doesn't stipulate courses that law schools should require for admission [source: LSAC]. Instead, preparing for pursuing a law degree as an undergrad amounts to a curriculum with a heavy emphasis on research and writing.
Since attorneys write legal briefs and opinions, as well as perform expert research on precedent-setting legal cases, undergraduate coursework that incorporates these two concepts will help bulk up a law school applicant's resume. Majors and minors in history, economics, political science, English and many sciences use these skills. Philosophy is also a good undergraduate pursuit for law school, as it teaches the logic used in law.
People who are opting for a law degree after they've already graduated and spent time in the work force shouldn't fret: Law schools are famous for accepting nontraditional students as well.
In addition to studies, law schools generally look for candidates who have either a number of interests or one or two areas of deep interest that have been pursued for a number of years -- if not a lifetime. Which of these will make it likelier that you're accepted depends on the goals of the school. Some law schools look for well-rounded students with a number of established interests. Other schools seek to cultivate a well-rounded campus, by assembling students that have demonstrated long-term interest in a single activity.
Demonstrating interest is what many law schools refer to as evidence of leadership and engagement. Some pursuits may be more applicable than others. For example, membership in debate clubs from a young age signals an applicant who can withstand the rigors of cross-examination.
With a robust transcript and resume under your belt, you're going to want to get the LSAT handled, too.