There are quite a few different ways to cite resources in your paper. The citation style usually depends on the academic discipline involved. Check with your professor to make sure you use the required style, and whatever style you choose, be consistent.
The Columbia College Library has put together a Citation Styles Guide to assist students with citing in the MLA, APA, and Chicago/Turabian formats.
The Columbia College Seabrook Writing Center has an Essay Writing Assistance page which provides useful info on MLA and APA documentation, among other writing tips and suggestions.