When in doubt about citation style, first consult the style guide in question. Style guides for ALA, MLA, Chicago, Turabian, ACS, the Associated Press, and more are available at the Writing Center.
If you still need help with citations, consult a Writing Center staff member or a librarian. The following sites are also helpful:
Purdue OWL (APA, MLA, Chicago/Turabian)
20-minute tutorial on APA style
University of Southern Mississippi's style guide page
Citation Styles portal by Ithaca College Library (check out the MLA "Cite Like the Devil" guides!)