Before you choose your citation style, you should take note of any preferences your instructor may have. For ENGL 122 and ENGL 223, the choice may well be up to you. But for history, psychology, science, or other classes you may be taking, there may be a prescribed citation style. If so, defer to your instructor's preferences.
If, however, citation style is up to you, look to your academic discipline for guidance in choosing your citation style. The subject of your paper and its intended audience may also have some sort of bearing on your choice of style. Here are some examples of disciplines for each of the three styles discussed here, for more information on the differences between each citation style check out the resources available at Purdue OWL.
This page will provide information about the most commonly used styles as well as tools to help you answer questions.
