For general and literature citations, prefer the MLA (Modern Language Association) format. Selected MLA style guides and resources:
Research and Documentation Online - a guide to research and MLA citations by Diane Hacker
City Source from Trinity College: MLA: The same site from Trinity gives examples of MLA style.
The OWL (Online Writing Lab) at Purdue University: A comprehensive resource, including MLA style examples.
University of Georgia Libraries Style Guides. Includes links to MLA and Chicago examples.