Then brainstorm keywords for each concept. Think of synonyms or related terms. A thesaurus, dictionary, or your textbook can be useful when thinking of related terms. Sometimes broader or narrower terms can be helpful too.
Why brainstorm? When searching, it's hard to know what words authors will use when they're writing about your topic. It's a good strategy to have a list of possible keywords ready so you can swap out terms as you search and hopefully get more and/or better results.
clinical terms versus lay terms
myocardial infarction vs. heart attack
neoplasm vs. cancer
acronyms versus the term(s) spelled out
HIV vs. human immunodeficiency virus
HIPAA vs. Health Insurance Portability and Accountability Act
variations of a term
ultrasonography, ultrasound, sonography
The way you combine your keywords in a search can make a big difference in the quality of results found.