Many databases provide citation which you paste into your paper.
Explains format of a citation and the basics MLA, Chicago, and APA citation styles.
If you know the elements of a citation, author, book titles, etc. you can use the Citation Builder to format citations in APA or MLA style.
EndNote is a stand alone citation manager used by researchers in the hard sciences and medicine. It is freely available to MU students, faculty, and staff. The Libraries teach introductory courses on EndNote.
Zotero is a free citation manager that started life as a plug-in for Firefox web browser. It has recently developed a stand alone product as well. The Libraries teach introductory courses on Zotero.
Mendeley is a free citation manager.