What is plagiarism?
The Northeastern University Academic Integrity Policy  defines plagiarism as
...using as one’s own the words, ideas, data, code, or other original academic material of another without providing proper citation or attribution. Plagiarism can apply to any assignment, either final or drafted copies, and it can occur either accidentally or deliberately.
Since it is a serious violation of intellectual integrity, plagiarism harms the reputation of the university as well as the individual. It is an academic integrity violation and is subject to Office of Student Conduct and Conflict Resolution (OSCCR) review.
Because the consequences are serious, and because ignorance of Northeastern's Academic Integrity Policy is not an excuse, it is important to learn how to give credit where it is due, which is known as "citing" or "attribution."
The following sources require citation:
- Word-for-word quotations from a source, including another student’s work.
- Paraphrasing (using the ideas of others in your own words).
- Unusual or controversial facts not widely recognized.
- Audio, video, digital, or live exchanges of ideas, dialogue, or information.
See concrete examples here: Plagiarism: what it is and how to avoid it.  (Indiana University)
How to avoid plagiarism
Citing and documentation adds considerable time to the composition of a paper. Always give yourself plenty of time to work on a paper, composing the bibliography and inserting footnotes as you go along.
As you work, keep careful records of where the ideas in your research come from by taking good notes, highlighting, using tools such as Evernote, keeping original printouts or photocopies and backing up files.
- Record the author, title, and publication information of what you read.
- Write down or highlight the URL if you include information from the Internet.
- Don't discard the information or notes you have collected until the paper has been graded and returned to you.
Remember that the only time that you don't need to cite a source is when an idea is either common knowledge or your own creation.
Examples of common knowledge that do not require citation:
- George Washington was the first President of the United States
- Carl Rogers was a psychologist, and his theory of client-centered therapy has a great impact in the field of psychotherapy.
Examples of your own creation:
- In 2003, I experienced the coldest winter of my life.
- In this paper, I argue that Plato's republic is a profoundly antidemocratic work.
Know how to cite
Become familiar with documentation guidelines, such as APA, MLA, etc., and find out the documentation style used in your discipline.
Both cite and document
When quoting or paraphrasing ideas, theories, data or words that were created or authored by someone other than you, make sure that you both cite them in the text, and document them in the "works cited" or bibliography at the end of your paper.
Anti-Plagiarism Strategies for Research Papers  by Robert Harris
Provides ideas on designing a curriculum that prevents students from plagiarizing, also covers detection tools.
TurnItIn is a plagiarism detection service available through Blackboard. Use TurnItIn to collect papers and assignments from the students by creating TurnItIn Assignments using the Control Panels of your Blackboard course. Once the work is collected from your students is is automatically compared to a variety of sources including the Internet and other papers that have been submitted in the past. More information is available from the Campus Information Systems Help Desk  at x4357.