Good question. Lawyers are required to take a legal research and writing class, or classes, in law school. Instructors devote a course that often takes the entire school year to teach students the basics of legal research and writing. There are books that explain the rules for legal citation, including The Bluebook: A Uniform System of
Citation. It is called the Bluebook because it has a blue cover. As it says on its website, http://thelegalbluebook.com, the Bluebook continues to provide a systematic method by which members of the profession communicate important information to one another about the sources and legal authorities upon which they rely in their work.
The Bluebook is not the only legal citation book. Two other popular legal citation books include: The University of Chicago Manual of Legal Citation often called the maroon book because of its maroon cover and Mary M. Prince’s Bieber Dictionary of Legal Citations: A Reference Guide for Attorneys, Legal Secretaries, Paralegals and Law Students.