Consult your school or department's referencing guidelines to find out what style you should use. Some institutions won't care as long as you're consistent. Others will insist on a particular referencing format.
Compile your citation data. Every statement you make in your essay that relies on the research of another writer will require a reference. You'll need to know the name of the author as well as any editors, the title of the book, the page number of the reference, the publisher and the date and place of publication. When collecting reference material, make sure to note these down.
Cite authors as you write your essay. Wherever you make a point that is drawn from the work of one of the authors you have read, cite it. Depending on the referencing style you use, this may take the form of an in-text citation, usually in parentheses, or a footnote or end note.
For example, if you were using an in-text citation format such as the Harvard style, you might cite an author as follows: "Production increased 40 percent within 5 years (Jones 2011, p. 1)". This citation format gives the author, date of the publication and page number, allowing the reader to find it in the bibliography.
Alternatively, if using a footnoted-style such as the Modern Language Association Style, you would follow the reference with a footnote number. The footnote at the bottom of the page would read "Tim Jones, Shoe Production in Interwar Poland (London: Faber and Faber, 2011) 1." The title of the book is underlined in this style. This format gives more complete bibliographic data without the reader having to leave the page.
Credit authors with arguments. When you draw on facts from an author's work, a citation is sufficient. When describing a line of argument put forward by an author, you should also mention them in the text. Explain that they originated the argument with a phrase like "according to."