Use the correct bibliographic style to create your bibliography. Each bibliographic entry, as well as the whole bibliography page, must be formatted correctly. Ask your professor which style is required. Some professors insist on one style; some don't care if you are consistent. See the guides to some of the most common styles at the links below.
You can also use RefWorks to store your bibliographic data and create bibliographies in any style. Sign up for a free account that you can use throughout your college career and even after graduation.
Historians use the Chicago Manual of Style. To access the latest edition, click on the link at the bottom of the page.