Look for the 'Peer-reviewed' or 'Scholarly Journals' button on a databases search results screen. Editorials, opinions, commentaries, and book reviews will still appear even though they are not peer-reviewed articles.
Still unsure if your journal is peer-reviewed? Use Ulrich's Periodicals Directory and look for the Referee jacket to confirm!
Google Scholar is a great tool for completing citations, locating known articles (e.g., from a Reference list or provided by a teacher), and for cited reference searching.