Chicago Manual of Style
If you are asked to follow the Chicago Manual of Style, you can either buy a copy or subscribe online. Sometimes having things at your fingertips on the web can be more convenient than looking them up in a book. Take a look and see if this type of reference works for you.
I was a history major, so I have about 6 copies of the Chicago around my house. Imagine my chagrin when, years out of college, I discovered Son of Citation Machine.
http://citationmachine.net/
This site lets you enter some info about your source and then it automatically finesses it into any citation style you choose. The site is no substitute for all the er… fascinating style essays you can find in the Chicago Manual and its ilk, but it does in a pinch.
(Warning – I haven’t had the occasion to use this site, so don’t hold me responsible if it spits out a bad citation. I would advise checking Citation Machine citations against the book before turning anything in.)