If you have a case citation, you can go immediately to the appropriate case reporter and look it up by volume and then page number.
If you know the name of the case you are looking for, you can use a case digest as a name index to the case reporters. Each digest has a "Table of Cases," which lists cases alphabetically by name and gives citations.
The "Table of Cases" volumes are typically located near the end of each digest set. Look for your case name alphabetically in the appropriate volume. If your case is very recent, you may need to check the volume's supplement or "pocket part" (the paper booklet inserted in the back pocket of the bound volume), which contains the most current information.
If your case is fairly well-known, you can use a legal periodical index, such as Index to Legal Periodicals or LegalTrac. Input some of the words from your case's name. For example, input the words roe wade as a keyword search if looking for the citation for the Roe v. Wade case.