The website of the National Archives and Records Administration (NARA) contains a National Archives Court Records guide. The guide provides helpful information for identifying which National Archives Federal Records Center holds the records for the court you are researching. This is especially helpful in researching the records for older cases not available from online sources such as Bloomberg Law, Lexis and Westlaw.
The NARA web page, Obtaining Copies of Court Records in the Federal Records Centers provides instructions and a link to the Order Reproductions page. Click on the "Frequently Asked Questions" tab in the upper left corner to find information of ordering civil case files, criminal case files and Court of Appeal case files.