Always ask your instructors which style they prefer. As you take more and more classes in different departments though, you'll notice that certain disciplines tend to use certain styles. So, if you're taking English 10, chances are you'll need to use the Modern Language Association (MLA) style. If you're taking Psych 10, you'll probably need to use the American Psychological Association (APA) style. Whichever style you choose, be sure to use it throughout your paper—be consistent.
Need more? See Resources for UCLA Students.
An instructor assigned his class to attend a concert and write an original review. When grading the students' work, he was struck by a particularly eloquent review of a B.B. King performance and was impressed by the student's insightful comments. As the instructor read on, he was struck again when the student elaborated on B.B. King's "slim build" and "youthful appearance." The instructor googled a few phrases from the student's review and in 0.2 seconds, there it was—the eloquent insightful review of a 1962 B.B. King performance as written by...well, not the student since he hadn't even been born yet. True story.
Anonymous. "Re: Your Student's Plagiarism Case & College Library Tutorial." 5 Aug. 2003.