Basic Example in Chicago Style
Chicago style is often used in history papers. It uses numbered footnotes. The exact format of the footnotes will depend on the type of source that you are citing, such as a book, journal article, newspaper article or archival source. Here is a generic example of a footnoted citation of a journal article:
The difficulty of citing properly is well-documented.[1]
[1] Smith, Bronwyn H. "Citations and Footnotes." Bibliography Quarterly (2005): 16-38.
Getting Citations directly from Databases - WORKS FOR SECONDARY SOURCES; generally NOT PRIMARY
Most online book/article databases provide citations automatically that you can cut/paste into your paper. Examples:
Citation Tools & How-To Guides - USE THESE SUGGESTIONS FOR PRIMARY SOURCES
OWL @ Purdue Guide to Chicago Style
Simple guide to Chicago - recommended. Describes not just citation styles, but also how to format your paper, etc. Guidelines on non-published archival material like letters and diaries is here; Guidelines on newspapers are here. Look at the "N" (for "note / footnote") guidelines. The "B" guidelines refer to stand-alone bibliographies.
EasyBib
This is one of several free online citation generators that will create citations that you can cut-and-paste into your paper. BE CAREFUL to use the correct tab (Book, Journal, etc.) and proofread the results!
Zotero
Very cool free app that lets you grab citations from anywhere online with one or two clicks, plus has lots of other features, such as formatting entire bibliographies, note-taking tools, online back-up, integration with Word, etc. Very nice but does have a learning curve.