An online source explaining all four of the most used citation styles is at Online! A Reference Guide to Using Internet Resources. Two copies of the book ONLINE! are located in the Library. Both of these resources show how to cite the sources you will need to list in your bibliography, works cited and footnotes in: MLA style, APA style, Chicago style, and CBE (biology) style. Another excellent site is Citing Sources, Guide to Library Research at Duke University.

Great citation help is available at Citation Style Guides , provided by the Ohio State University Libraries, and Writer's Handbook -- Documentation Styles, maintained by the Writing Center at the University of Wisconsin-Madison.

For APA: American Psychological Association, these are helpful:
APA Style Guide from USM Libraries
Electronic Reference Formats Recommended by the APA - from APA's style guide web site

For the proper procedure for citing in a biological science format, the following are useful sites for CBE style:

Writer's Handbook of U. of Wisconsin-Madison Writing Center
Monroe Community College writing guide