Citation styles are usually chosen for you.  If you are writing a paper for a class, your professor may specify which style you should use.  If you are submitting a paper to a journal, you should use their designated style.

If you are allowed to choose for yourself, think about your discipline (or major):

Your discipline (or field) might have a preferred citation style.  It is a good idea to ask your professor if there is a style typically used in your field.

      • APA (American Psychological Association) is used by many fields in the social sciences, psychology, and education.  It is also used in some OSU courses in the sciences.
      • MLA is widely used in the humanities, and in most writing courses at OSU.
      • Chicago/Turabian is used in many disciplines at OSU.  It is very common in history courses. 

If you want to look up the standard style(s) for your field, this list at Purdue's Online Writing Lab is quite comprehensive.