Identifying the essential keywords is the most important task. Be sure to brainstorm and think of additional related keywords you might use: instead of "health benefits" substitute "nutrition" and see how that changes the results (organic food and nutrition).
If you find a good article, look at the subject heading/terms in the record -- click on a relevant subject term for more focused results.
Remember, the database is simply looking for your search term(s) across many fields, regardless of its meaning. A search using the term "race" will return articles dealing with racial issues, but may also retrieve articles about a NASCAR race or political race. Choose your search terms carefully.
The librarians will be glad to help you find articles. Visit the Ask a Librarian page for contact information.