Anthropologists and some other social scientists use Chicago Author-Date.
Biologists and some other scientists use CSE.
Scholars of English and other literatures use MLA Style.
Geologists use GSA Style (PDF).
Historians and some other humanists use Chicago Notes & Bibliography.
Scholars citing legal materials use Bluebook Style.
Mathematicians use AMS Author LaTeX packages.
Scholars of Politics use APSA Style.
Psychologists and some other social scientists use APA Style.
Some scientists use styles required by specific journals, like Ecology.
Sociologists use ASA Style.
Ultimately, your professor is the one who decides which citation style is appropriate for your paper.
Stop by the Research Desk in Ladd Library, and a librarian can help you learn how to build your bibliography.