The most commonly used publication styles are created by the Modern Languages Association, the American Psychological Association, and the University of Chicago. See the invidival tabs for Chicago, APA, and MLA for citation examples and further information.
(No matter what style your professor requests, a citation manager can help you organize and cite your sources, and so can a librarian.)
Zotero: The Tri-College Libraries recommend Zotero, a free tool that can format your bibliography, keep your citations organized, and even save your articles in the cloud so you can access them later from the library, home, or a cafe.