Great question! When I went to law school, I really did not know what field of law I wanted to study; I just knew that it was a good education that has broad applications in many different areas. Although law school does help to narrow down the choices because you can take classes in the various fields, knowing a little about the legal profession and what you can do with a law degree can help you determine what law schools you want to apply to, where the best likelihood of getting a job is, etc. There is a lot of information available online, but I did a quick check that describes several legal fields and found this site helpful:
Your college or university will also have a career development office, and that's a good resource that you can use to research jobs and careers. You could also use this office to connect with Alumni in various professions and see if they will do informational interviews so you can ask them about their jobs and how they got there. Don't be shy! People like talking about their experiences and you can learn so much this way. A part-time job or internship is another way to learn about what happens on a day-to-day basis in any given job. It's a great way to learn about what you might want to do, or what you might not be interested in doing for a career. Hope this helps...good luck to you!