There are many different "styles" you may choose from when citing sources. Your professor will probably tell you which "style" is preferred for your class. MLA (Modern Language Association), Chicago, and APA (American Psychological Association) are the three which are used most often by students at The Claremont Colleges.
The Chicago Manual of Style (CMS) covers a variety of topics from manuscript preparation and publication to grammar, usage, and documentation. The material focuses on one of the two CMS documentation styles: the Notes-Bibliography System (NB), which is used by those in literature, history, and the arts. The other documentation style, the Author-Date System, is nearly identical in content but slightly different in form and is preferred in the social/sciences.
Citation Managers are tools to help you keep track of your citations as you research and to create/format your citations and bibliography. For example, Zotero allows you to keep citations, full text articles, and other research resources organized in one place. You can also use these tools to format your bibliographies and the notes/citations in your papers according to the appropriate style (APA, MLA, Chicago, etc.).
Zotero is a free open source application that works with Firefox, Chrome, and Safari, you can also download a client to your computer. It is a good choice if you use just one computer when researching. You can access citation information when online or offline.