Common knowledge is facts that can be found in numerous places and are likely to be known by a lot of people. You don’t need to document sources for these facts.
Because the following is a commonly known fact, it doesn’t need to be cited:
John F. Kennedy was elected President of the United States in 1960.
In the following, you do need to cite your source because the idea that "Bush's relationship with Congress has hindered family leave legislation" is an interpretation of facts:
According the American Family Leave Coalition's new book, Family Issues and Congress, President Bush's relationship with Congress has hindered family leave legislation (6).
Use quotations when using someone's exact words. When you quote, place the passage you are using in quotation marks, and document the source according to a standard documentation style (MLA, APA, etc). The following is a correctly cited quotation:
According to Peter S. Pritchard in USA Today, "Public schools need reform but they're irreplaceable in teaching all the nation's young" (14).
Paraphrase is using someone's ideas, but putting them in your own words. This is probably the skill you will use most when incorporating sources into your writing. Although you use your own words to paraphrase, you must still acknowledge the source of the information.
If Pritchard says “Public schools need reform but they're irreplaceable in teaching all the nation's young” you are plagiarizing if you write:
Public schools need to be reformed, but we can’t replace public schools’ roles of teaching youth in the United States.
Credit Pritchard and use new words and a new sentence structure, and you can avoid plagiarizing. This is correct paraphrasing:
Pritchard admits that public schools are the best approach to educating children in America, despite his demand to improve the system (14).
A paraphrase should contain all of the author's information and none of your own commentary. Even if you have avoided using the author's words, sentence structure, or style, an unattributed paraphrase is plagiarism because it presents another person’s ideas as your own.
To avoid plagiarism, you must give credit whenever you use:
According to Smith...
In his 1987 study, Robinson proved...
The St. Martin's Handbook defines plagiarism as "the use of someone else's words or ideas as [the writer's] own without crediting the other person" (Lunsford and Connors 602)