Thorough legal research on a topic involves studying federal and state laws (statutes/statutory law), regulations (administrative law), and court decisions (case law). The recommended websites below provide access to topic overviews, which summarize the laws related to various topics and include links to primary sources -- related statutes, regulations, and court decisions. These overviews are a great starting point for your research.
LexisNexis provides access to the text of federal and state statutes and court decisions, as well as reference materials like legal encyclopedias.
For a more thorough explanation of how to conduct legal research, check out this great guide from the Georgia State University Law Library: