Remember to cite not only direct quotes, but also other people's ideas. If you paraphrase something, changing a few words to make it sound less like a direct quote, you still have to cite it. If you are uncertain, it is better to cite a source than to be accused of plagiarism for not citing something you should have.
Publication Manual of the American Psychological Association (http://suncat.csun.edu/record=b2499930)
Reference Room BF76.7 .B83 2010
Reserve Desk BF76.7 .B83 2010
Floor2 BF76.7 .B83 2010
APA Style Guide (PDF) by Eric Garcia