A Manual for Writers of Research Papers, Theses, and Dissertations
by Kate L. Turabian; Wayne C. Booth (Revised by); Gregory G. Colomb (Revised by); University of Chicago Press Staff (Revised by); Joseph M. Williams (Revised by)
Probably the best, free source of online help for writing and citing.
Citation Management Software - Zotero
If you choose to use citation management tools such as Zotero or EasyBib, remember that they aren't perfect systems. Consult your style guides and double check the accuracy of all computer generated citations.