The specific format of your citations will depend upon the documentation style you are using. Different disciplines use different styles - always check with your instructor and/or syllabus for every class.
Commonly used styles include APA, MLA, Chicago, and Turabian. Each of these has an official style guide. These manuals contain detailed examples on citing a wide variety of sources. In addition, they contain information about proper formatting, such as margin and font size.
Some disciplines have their own discipline-specific citation style. Check with your instructors.
For most styles, you cite your sources in two places:
1) Within your paper (in-text citation) - immediately after using a source, include a parenthetical citation, footnote, or endnote.
2) At the end of your paper - a complete list of your sources known as a Bibliography, References, or Works Cited section.
Use software like EndNote and Zotero to manage your sources - download citations from library databases; export the bibliography into your paper. Compare the features of some different citation manager programs here.
Zotero is a free Firefox plugin that easily saves citations from most library databases, as well as sites like Amazon and the New York Times online.
Zotero has a Word plugin that automatically create bibliographies in the style of your choice.