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).
Use the Intergovernmental Organization Search Engine (a Google custom search) to search across hundreds of IGO websites:
Use the Non-governmental Organization Search Engine to search across NGO websites. Sites were chosen based on their consultative status with the United Nations Economic and Social Council (ECOSOC) and also collated from University of Minnesota Human Rights Library, Duke University Libraries' NGO Research Guide, and the World Association of Non-Governmental Organizations (WANGO).