The matter of picking a good major for law school is a pretty simple. You want a serious subject that interests you and where you think you can obtain a high GPA.
Now what do I mean by a serious subject? I mean one that is challenging and is well-regarded as an area of academic inquiry. This could be anything from English (Evan’s major) to Finance (Josh’s major) to Engineering to Philosophy. Generally, if it is a major where you tend to see serious students flock, you are in good stead.
This is important for two reasons: First, more difficult subjects are well-regarded by admissions staff. Though it may surprise some, the hard science majors are particularly in demand at law schools. I think this is partly because they are in short supply and add variety to the class, but more so because these students tend to excel in the law school environment and also are very in demand for employment after receiving a law school education (often for intellectual property law).
Second, dense subjects just prepare you better for the rigors of law school. I noticed that students who did hard majors at rigorous schools had a slight edge in law school because they were used to dealing with a very heavy workload.
On the other hand, students from the humanities such as English, philosophy, or history, had plenty of opportunity in undergrad to develop the critical thinking skills and communication skills that served them well in your first year legal writing class, on law school exams, and especially later in the practice of law. Admissions staff know that these majors are valuable training and admit them to top law schools in large numbers. Just as an aside: take a logic course in your school’s philosophy department, as it gives you a priceless head start on your LSAT study.