Different disciplines use different citation methods. Here are the five most common ones:
APA: American Psychological Association. Frequently used in the sciences and social sciences. Consult the Publication Manual of the American Psychological Association.
MLA: Modern Language Association. Frequently used in the humanities, literature, and arts. Consult the MLA Handbook for Writers of Research Papers (for undergraduates) or MLA Style Manual and Guide to Scholarly Publishing (for grad students).
Turabian: Multidisciplinary; frequently used in history. Consult A Manual for Writers of Term Papers, Theses, and Dissertations by Kate Turabian.
Chicago: Multidisciplinary; frequently used in history. Consult the Chicago Manual of Style.
AMA: American Medical Association. Frequently used in health, medicine and biology. Consult the American Medical Association Manual of Style.