You must cite your source of information any time you use another person’s ideas, opinion or theory. You must also provide citations for any facts, statistics, graphs, or drawings that are not common knowledge. Quotations of another person's actual spoken or written word and paraphrases of another person's spoken or written words must also be cited.
Purdue University's Online Writing Lab has one of the best websites devoted to academic writing and citing sources. With definitions and examples, visit the site to learn how to create an annotated bibliography.