There are thousands of cases filed and decided every day. Where can we find the ones we need for precedent? That depends on your jurisdiction -- is it State or Federal? Federal cases are all published chronologically in the Federal Reporter (F.; F.2d; F.3d), which is available online for free here and here. You can also find the print version at your local law library. The books like like this:
State cases are also published chronologically in various Reporters based on region. They are:
Pacific Reporter(P.2d; P.3d):Alaska, Arizona, California, Colorado, Hawaii, Idaho, Kansas, Montana, Nevada, New Mexico, Oklahoma, Oregon, Utah, Washington and Wyoming.
Atlantic Reporter (A.; A.2d; A.3d):Connecticut, Delaware, the District of Columbia, Maine, Maryland, New Hampshire, New Jersey, Pennsylvania, Rhode Island, and Vermont.
Once you've found the appropriate Reporter, how do you use it? A typical case citation will lead you directly to the correct volume and page.
As you can see from the image above, the first number in a citation tells you the volume number, the letters in the middle tell you which Reporter, and the last number is the page number within that specific volume.
As always, if you ever have any questions, ask your local librarian!