Is it still plagiarism if I didn't intentionally copy someone else's work and present it as my own, that is, if I plagiarized it by accident?
Yes, it is still plagiarism. Colleges and universities put the burden of responsibility on students for knowing what plagiarism is and then making the effort necessary to avoid it. Leaving out the quotation marks around someone else's word or omitting the attribution after a summary of someone else's theory may be just a mistake (a matter of inadequate documentation) but faculty can only judge what you submit to them, not what you intended.
If I include a list of works consulted at the end of my papers, doesn't that cover it?
A works-cited list (or bibliography) tells your readers what you read but does not indicate how and where this material has been used in your paper. Putting one or more references at the end of a paragraph containing source material is a version of the same problem. The solution is to cite the source at the point that you quoted, paraphrased, or summarized it. To be even clearer about what comes from where, also use what are called in-text attributions. See the next FAQ.
What is the best way to help my readers distinguish between what my sources are saying and what I'm saying?
Be overt. Tell your readers in the text of your paper, not just in citations, when you are drawing on someone else's words, ideas, or information. Do this with phrases like "According to ..." or "As noted in ...", so-called in-text attributions.
Are there some kids of information that I do not need to cite?
Yes. Common knowledge and facts you can find in almost any encyclopedia or basic reference text generally don't need to be documented (that is, John F. Kennedy became president of the United States in 1960). This distinction can get a little tricky because it isn't always obvious what is and is not common knowledge. Often, you need to spend some time in a discipline before you discover what others take to be known to all. When in doubt, cite the source.
If I put the information from my sources into my own words, do I still need to include citations?
Yes. Sorry, but rewording someone else's ideas doesn't make it your own. Paraphrasing is a useful activity because it helps you to better understand what you are reading, but paraphrases and summaries have to be documented and carefully distinguished from ideas and information you are representing as your own.
If I don't actually know anything about the subject, is it okay to hand in a paper that is taken entirely from various sources?
It's okay if (1) you document the borrowings and (2) the assignment called for a summary. Properly documented summarizing is better than plagiarizing, but most assignments call for something more. Often comparing and contrasting your sources will ideas, so that you can have something to contribute. If you're really stumped, go see the professor.
Is it plagiarism if I include things in my paper that I thought of with another student or a member of my family?
Most academic behavior codes, under the category called "collusion," allow for students' cooperative efforts only with the explicit consent of the instructor. The same general rule goes for plagiarizing yourself, that is, for submitting the same paper in more than one class. If you have questions about what constitutes collusion in a particular class, be sure to ask your professor.
What about looking at secondary sources when my professor hasn't asked me to do this? Is this a form of cheating?
It can be a form of cheating if the intent of the assignment was to get you to develop a particular kind of thinking skill. In this case, looking at others' ideas may actually retard your learning process and leave you feeling that you couldn't possibly learn to arrive at ideas on your own. Professors usually look favorably on students who are willing to take the time to do extra reading on a subject, but it is essential that, even in class discussion, you make it clear not to present others' ideas as your own. In class discussions, if you bring up an idea you picked up on the Internet, be sure to say so explicitly.
David Rosenwasser & Jill Stephen, Writing Analytically, Third Edition, Thomson/Heinle, USA, 2003, p. 177.