The two most popular writing citation styles are the Modern Language Association (MLA) and American Psychological Association (APA) styles. Typically, MLA style is used in the humanities, whereas APA is used for scientific and journalistic articles. Depending on your major or area of concentration, you may only need to use one style, but it’s actually important to understand both styles in case you run into a professor who requires something different.
From experience, I spent most of my Master’s program using MLA style, but I took two communications courses that required APA style. The Purdue OWL’s website became my best friend when trying to translate MLA citations to APA for those papers. Although many classes include a current copy of MLA or APA style guides, I strongly advise against purchasing a textbook version of any style guide because they are updated periodically. You can find plenty of resources free online, which saves money, space, and trees.