It depends on which area of law you wish to go into. If you are trying to go to law school after college, there is no specific minor that law schools will require you have. However, different minors such as political science, history, international studies, or business may provide some insight into what you will learn in law school. In general, the best thing to do in preparation for law school is to maintain a strong GPA and do well on the LSAT (law school admissions test). It is also important to remember that no major or minor will prepare you for for law school significantly better than any other. Think about what you would like to do with a law degree and minor in something that relates to that field. If you want to work in business law, take business classes, as they will prepare you for working with business clients.
If you are interested in working in a different area of law such as law enforcement, you may need to take criminal justice classes or something specific to that area.