Throughout the research process it is important for you to keep track of your information sources. Fortunately, many of the electronic databases you will be using (including QCAT) offer you the option to download, print or email the citations to the material you find. This is a great way to keep track of the information you're considering.
Citing sources is a key part of your research: it documents what sources you have used in writing your paper and gives credit to an author's work that you have used. It also gives information to identify and retrieve the cited sources. Another one of my favorite resources is the Online Writing Lab ('OWL') at Purdue University. There you will find step-by-step guidance to citation for MLA, MLA and Chicago.