Secondary sources help to situate your thesis in the framework of larger scholarly conversations. Identify scholars whose work you will engage with early on in your research process.

As you search through library catalogs and databases, take note (literally, make lists) of the keywords and terms that you find useful, as well as the Library of Congress Subject Headings associated with your topic. The subject headings will be the same in other library catalogs and databases, and that language provides crucial keyword searching terms.

When you are searching in library catalogs for book length studies about your topic, remember to search more broadly than your topic as well as in narrower related sub-topics. Many book-length secondary sources will not require reading in entirety. Use tables of contents and indexes effectively to identify crucial chapters and passages. 

Peruse the bibliographies and footnotes in your secondary sources; this will help you find additional relevant secondary sources and may direct you to primary sources in archives, published sourcebooks, databases of primary source collections, and elsewhere. Also take note of dates/events, organization names, personal names, names of particular policies, laws or initiatives etc.; all of these are potential keywords for finding primary sources.