1. Try the "agency approach." Who produces the information you need? How is this information organized and disseminated? If you can answer these questions, you can create a much more targeted, focused search.
2. Google like a pro. To limit your Google search to government websites, use the very powerful "site:" search. You can search all .gov websites (site:gov) or narrow your search to a particular agency's website (site:cdc.gov).
The Federal Register is the official daily publication for rules, proposed rules, and notices of Federal agencies and organizations. It also includes executive orders and other presidential documents.
Federal Register: unofficial XML-based prototype of the daily Federal Register, organized and displayed in an easier to read format. Includes web tools and user aids designed to make it easier to understand and participate in the regulatory process.
Federal Register (official version, 1994-current, Government Printing Office)
For more in-depth information about regulatory research, please see this guide to "Rules and Regulations".