Once you have your question, look over it and decide which words are the keywords – the words most important to capturing the question's meaning. Underline or otherwise highlight those words.
Then, for each keyword, try to think of other possible words that have the same or similar meanings, and list them. These synonyms will be useful for doing more complete searches, regardless of what terms are used in a given article. For example, if you are interested in car crashes, you would want to find articles that use the terms "car crash," "automobile crash," "auto crash," "car accident," "automobile accident," etc..
To continue the example, the student selected some keywords and thought of possible synonyms. The list of synonyms is not exhaustive, nor need it be at this point.