Library databases are organized around concepts and to effectively search a database you should first identify key concepts based on your research question or topic. Once you know the concepts you're researching, you can begin brainstorming keywords that you will use to search. Be sure to think of some keywords that are broader than you topic and some that are more narrow.
Example Topic "How have fairy tale princesses evolved in the last 250 years?"
Concepts: female representation & fairy tales & 1760-present