Search names of people you read about, when they appear as authors, it's a primary source:
Keep lists of synonyms for keyword searching
For example:
middle ages, dark ages, medieval
barbarian, anglo-saxon (other individual group names)
church, catholic, christian, chrisitanity (christian*)
monk, monastic, relgion, religious (religio*)
constantinople, byzantine, byzantium, instanbul
Searching the catalog using a variety of keyword vocabulary will lead you to a broad selection of primary sources.
Consider WHAT type of primary sources were produced in the period you are researching. Additionally, which type of source would most likely provide perspective on the historical theme you wish to explore.
consider WHO wrote the sources. For example if you're researching late Byzantium and the Ottoman Empire, there are sources by:
Look at the catalog record for a primary source or sourcebook on your syllabus or on Course Reserves. Click on the Subject Headings to find more titles with the same subject heading.
Watch for these words in the Subject Headings - they are Library of Congress Subject Heading controlled vocabulary indicating primary sources
sources, letters, interviews, speeches, personal narratives, diaries, correspondence, sermons, notebooks, sketches, description and travel, treaties, pamphlets, biography (includes memoirs), newspapers, periodicals, pictorial works, art, architecture, portraits, caricatures and cartoons, cookery, decorative arts, furniture, material culture, guide books, maps, fiction, poetry, periodicals, newspapers, bibliography, early works to 1800
Use them in keyword searches in the library catalog: example (pope or papacy) AND (sources or correspondence)
This is one research technique, but not a perfect system. Most topics fall under multiple Subject Headings. Many wonderful sources at Vassar do not have Subject Headings indicating they are primary sources.