Every essay, term paper, research paper, or book review should be written in a specific format. Usually, when you receive an assignment from your professor he specifies which format the essay should follow. But in some cases the format is not provided and you have to be aware how your essay should be structured. Below, you will find the most popular citation styles and the guidelines on how to use them.
MLA Format: literature, arts, and humanities.
APA Format: psychology, education, and other social sciences
AMA Format: medicine, health, and biological sciences.
Turabian Format: developed for college students to use with all subjects.
Chicago Format: used with all subjects in the real world by books, magazines, newspapers, and other non-scholarly publications.
There are some sample essays in the above formats which can be downloaded here.