From the University of Bergen
There are three ways to properly use another author's words or ideas:
Use quotes when you wish to retain the exact wording of the author. Quotes should be used sparingly, and shouldn't come from only one information source. You should also strive to maintain the author's intent--using ellipticals to remove pieces of the quotation that you disagree with is unethical.
Quotes are best used:
Quotes must be word for word, enclosed in between " ", and must be credited to the original author.
Paraphrasing involves taking the source material and putting it into your own words. The paraphrased portion should be about the same length as the original, and should maintain the original source's meaning, as well as all of the details. Be careful when paraphrasing--changing just a few words or changing the sentence structure slightly is not paraphrasing, it is plagiarizing.
Good paraphrasers will read the source material, pull out the main points, and using their own words (without adding personal opinions or ideas) convey these main points to the reader. Paraphrased information must also include an attribution to the source of your information. Paraphrasing is best used:
Summarizing condenses the original piece of information, in your own words. When should you summarize? Summarize the information you're using when details are less important, and when you want to present an overview of the information. Good summarizers will read the text, pull out the most important pieces of information, and using their own words, will present these pieces of information to the reader. Summarizing is best used:
Still unsure? Decide When to Quote, Paraphrase, Summarize can help.
Common knowledge, or "what everybody knows", is the only thing that does not need to be cited.
How does one know, however, "what everybody knows"?
In one field, a fact that is considered "common knowledge" to someone within that field, will not be considered common knowledge to someone outside of the field.
Generally, for a fact to be considered common knowledge, it has to meet two criteria:
Ideally, it should meet a third criteria--that is, the fact may be found in general reference sources--general encyclopedias or almanacs.
With controversial issues, common knowledge is factual and must involve agreement among most people. "It is NOT common knowledge that drilling will affect caribou migration or feeding habits." While evidence may exist to support this statement, there is not enough agreement to make it "common knowledge."
"How to Avoid Plagiarism: Common Knowledge." Cal State. Accessed 8 June 2012.