Evaluating the sources you find is a crucial step in the process of library research. The questions you ask about books, periodical articles, web pages, or multimedia sources are similar whether you're looking at a citation to the item or have the item in hand.
How to Prepare an Annotated Bibliography
Guidance for creating and formatting citations and annotations for an annotated bibliography.
Distinguishing Scholarly from Non-Scholarly Periodicals: A Checklist of Criteria
Shows how to evaluate periodicals by looking at their format, intended audience, and appearance.