"The University of Akron community regards academic misconduct as a serious matter. It is your responsibility to know what constitutes academic misconduct."
--UA Office of Student Judicial Affairs
Different disciplines use different styles. Below is a general guideline. However, you should ALWAYS check with your instructor about what style she or he requires for your papers. Typically, there will be a note about it in the syllabus or the assignment instructions.
MLA: Arts & Humanities (e.g., Literature and English Composition classes)
APA: Social Sciences (e.g., Communication and Sociology)
Chicago: Social Sciences (e.g., Anthropology and History)
There are also a number of other styles for very specific disciplines: ACS (Chemistry), IEEE (Engineering), AP (Journalism), Medicine (AMA), and more...