Search terms will depend on your topic of course, but generally you will want to use the most important words related to your topic or what we call keywords.
Brainstorm words related to your research question, like synonyms, or words that have the same meaning. Some sources may be using different words to describe the same thing.
Don't have a research question? Look at this page for a how-to and examples of research questions
Check out the Thinking Tool linked below, and the video on how to use it for a step by step process that can help you refine your topic and come up with keywords.
Now called Gale eBooks.
Multidisciplinary database of full text encyclopedias and reference sources for research and ready reference. Enables one search that covers all sources. Subjects include arts, sciences, medicine, and the humanities.