Do you already know about a case that deals with the issue you are researching? That case can be used as a springboard to find other relevant cases by:
Using Shepard's (Lexis Advance and Nexis Uni) or KeyCite (WestlawNext). Enter the citation for the opinion and then review the citing references, that is, later cases and other sources that cite to the known case. Note that you can limit the citing references by jurisdiction, court, treatment, and other parameters.
Using West Key Numbers (WestlawNext) by identifying the relevant key number that focuses on the specific issue you are researching. Click on the headnote and then select a jurisdiction to locate cases dealing with the same issue.
Check the Table of Cases volumes of the American Law Reports (ALR) to see if the known case has been cited in an annotation. If it has, then review the annotation to identify other cases on the same topic.
Try these tips:
Look at the major cases cited by the most relevant case you've found.
KeyCite or Shepardize those earlier cases to find other related cases.