Databases use controlled vocabulary to index or tag articles and books. Successful searching is dependent on discovering what those words (terms) are.
Some databases have tools to help you find the controlled vocabulary terms. These terms usually include definitions. For example -->
Take your topic and look for key concepts. Take those concepts and brainstorm related terms.
1) Identify a question or topic
2) Look for key concepts
How does fashion inform our understanding of gender in House of Mirth?
fashion OR dress OR style OR clothes
House of Mirth OR Edith Wharton
gender OR women OR men OR female OR lady
Use quotation marks to search for a phrase
Use a symbol (* is the most common) to look for variant endings of a word