Here are some of Census.gov's tutorials and other user aides:
These guides and other tools are developed by libraries and other organizations to help users with Census data. The Oklahoma Dept. of Libraries is particularly active in Census education. Here is their page: How to Use Census Data: Guides and Handouts About Data from the U.S. Census Bureau, which links to many of their training materials.
Daniel Cornwall, at the Alaska State Library, developed this useful set of guides to using Census 2000 data. While some of the information is specific to this Census, much of his analysis and explanation is more generally useful. Note that the documents are PDFs without working links.
Census.gov offers a great many resources to help users get the most out of their data. Some of their major portals, tutorials, and reference materials are listed in the boxes below.
In addition to these resources, the Census Bureau has a collection of web-based tutorials and training materials that can be found in their Training Resources Library.
Tips for using the FTP file repository
In drilling down through the file heirarchy on the FTP site, look for README files and others (especially PDF files) containing words such as:
These files can provide valuable information to help find the tables you need and understand the data they represent. Note that different parent directories contain different types of sub-directories and sub-files, so that a helpful file found in one directory might not appear in another one, or might be there, but be named something different.