Before attempting to conduct your search, take some time to prepare. Working your search out on paper first will help you sort through all of your ideas, and let you develop a clear search strategy that accurately dictates your information need.
Start by building up a search vocabulary. Write down your most important keywords and then try to come up with some other synonyms and related terms that are specific to your topic. Identifying these terms right from the get-go can help you better focus your research, and provide you with a greater pool of terms that can later be combined to yield you the most comprehensive results possible.