Is your patron working from a printed document? (homework assignment, textbook,
legal document, newspaper article) Ask to see it. You might find the clues you need to help your
patron (the name of the person who introduced a bill, case citation, reference to court rules,
violation written on the traffic ticket).
If your patron presents you with an incomplete citation or something that sounds like a popular name (ERISA) ask him to enlighten you on the context of the question--education students researching "Title 9" are usually referring to The Educational Amendments Of 1972, (PL 92-318 Title IX) prohibiting sex discrimination.
When your telephone patron requests you to "look up the law on..." ask him to supply you with keywords/subject headings and jurisdiction (local, state, federal, international). If you can't match his terms with the subject headings listed in the laws/regulations/digests/practice books, invite him to use the materials himself or offer to send him the table of contents/index pages. Gently remind him that you, the librarian, cannot select or interpret the law.
If your patron is unfamiliar with his legal topic suggest he begin with a subject-specific book/guide/FAQ written in plain language. Items published by Nolo Press , Legal Services of New Jersey, the New Jersey Institute of Continuing Legal Education (NJICLE) , local bar associations, courts and government agencies are often the easiest way for your patron to begin learning about his legal topic. Once he grasps the general process/procedure of the law he can then use the annotations to locate/update answers to specific questions.