1. Secondary sources can lead you to the leading cases, plus related propositions that you need to show to bridge to your main claim. 
2. Annotated codes provide many key cases that interpret a statute. However, they generally are not 100% comprehensive.
3. One Good Case Method
   • ​​​​Looking back: What cases are cited by the court in your One Good Case? 
   • Looking forward: Using a citator such as Key Cite/Citing References (Westlaw) and Shepard’s (Lexis), what later cases interpret the cases you intend to rely on? 
   • Looking out: Topical organizations (headnotes) categorize all published decisions, so a digest will give you good coverage of the universe of cases that exist. Identify Topic + Key Number or Headnote from leading case, or browse the Key Number System Outline on Westlaw. 
4. Keyword search: Use the keywords you discover by reading the earlier cases to construct an Advanced Search. Consider conducting Terms and Connectors searches and narrowing results by using /s, /p /n, or Term Frequency. 
5. Repeat the above as needed: When you find a new case, Shepardize or KeyCite it. Read it to see if it cites new cases. See if it provides a Key Number that you haven’t seen. Note whether it uses a new term for your issue that would make a worthwhile search. 
6. Final step: Shepard’s/KeyCite to confirm whether the cases are still good law. See the Determining if Case Law is Still Good page of this guide for additional details.

Determining this comes with experience and can depend on the issue or the court. The prevailing description is that when you keep seeing the same cases over and over again without anything new, you’re done. In general:

1. Use at least one source/search that involves an editor attempting to assemble like cases together. This may be the Westlaw Key Number system, Lexis headnotes, or an annotated code.
2. Use at least one online Boolean search to see if cases exist that were not identified in your first source or were too recent to be indexed in any other system you used.
3. Shepardize or KeyCite every case on point (within reason depending on how many exist).
4. Read entirely every case that might provide new cases, that you might cite or that your opponent might cite, and that is from the highest court (within reason depending on how many exist).