Keywords reflect the main topics of your question.
It helps to brainstorm as many keywords related to your topic as you can.
There may be different keywords to describe your topic, and some library resources may use different terminology than what you think is the obvious choice.
Are there different words or phrases that describe what you are looking for?
Use a thesaurus can help you find synonyms.
You will come across useful search terms as you go.
Omit non-essential words, as they are very common and may not help narrow your search.
Try using keyword variants in different databases.