One of the ways in which we create new ideas is by relying on words that have been said or written before. It's ok to use others' words, but it is important to follow some best practices.
1. Reserve quotations for works framed in our minds as unalterable. e.g., famous speeches, documented laws, or religious texts.
2. Use quotations sparingly. Use too many and your own voice and ideas don't have room to shine through.
3. Always cite your sources. Citing your sources is not only the right thing to do, it is also how you avoid plagiarism.
What is paraphrasing?
Paraphrasing is, perhaps, the most common way to legitimately incorporate someone else's material into your writing. It involves a detailed rewriting of a passage from source material into your own words. Essentially, a writer will paraphrase when they want to incorporate someone else's idea into a paper without directly quoting (using quotation marks) them. A paraphrase must be credited to the original source.
When should I paraphrase?
You should consider paraphrasing when the wording of the original source is less important than the source. This will allow you to maintain a smooth continuity in your writing. Paraphrases are typically more detailed than a summary.
Consider paraphrasing to:
This material has been adapted from the University of Houston Victoria: Decide When to Quote, Paraphrase, and Summarize
What does paraphrasing look like?
In The Sopranos, the mob is besieged as much by inner infidelity as it is by the federal government. Early in the series, the greatest threat to Tony's Family is his own biological family. One of his closest associates turns witness for the FBI, his mother colludes with his uncle to contract a hit on Tony, and his kids click through Web sites that track the federal crackdown in Tony's gangland.
Fields, Ingrid Walker. “Family Values and Feudal Codes: The Social Politics of America’s Twenty-First Century Gangster.” Journal of Popular Culture 37.4 (2004). Academic Search Complete. Web. 13 Mar. 2012.
In the first season of The Sopranos, Tony Soprano's mobster activities are more threatened by members of his biological family than by agents of the federal government. This familial betrayal is multi-pronged. Tony's closest friend and associate is an FBI informant, his mother and uncle are conspiring to have him killed, and his children are surfing the Web for information about his activities (Fields).
This materials has been adapted from Purdue OWL's: Paraphrase: Write it in Your Own Words