Citation Style Guides
APA Style Guide
APA's web site, containing tips for tricky citations and sample papers.
AMA Manual of Style
You may also borrow copies of these manuals from the Course Reserves collection in the Library & Study Commons on the 4th floor of Building 38.
Here are a few of guides that can help you avoid plagiarizing.
Quoting, Paraphrasing, and Summarizing (Purdue OWL)
Principles of Paraphrasing (Harvard)
Incorporating References (University of Kanas)
Avoiding Plagiarism (Purdue OWL)
You may also want to talk with the MGH Institute's Writing Consultant.