For Web Sites: Check to see if the search engine has an "Advanced" feature. To refine your search, use search features, see: Google Search Features for examples such as synomyn searching, booean operators (AND, OR, NOT) and so on.
For Databases: Check the HELP function. Look for drop down menus, use field searching, thesarus, keyword searching features and boolean operators, truncation symbols & wildcard symbols to help narrow your search.
For Print Resources: Use the index and browse the Table of Contents to locate information. Use secondary resourses to begin your search. Secondary resources, such as legal treatises or law review articles often cite to case law, statutes, and other primary resources as well as provide expert advise on your topic.
If your research is for a specific jurisdiction, look for local material, digests, treatise, legal encyclopedias and periodicals. These are often most helpful for locating primary resources on your issue. In Wisconsin, the Wisconsin State Bar Association publishes practice materials written by attorneys for attorneys. In the Law Library this set is located behind the circulation desk in looseleaf binders and covers broad issues of law. Online this set can be found in Books Unbound.