When should you quote? When should you paraphrase?
First, remember that any paper that you write should be guided by your ideas and organization; the borrowed material is there to help support and lend credibility to any points you want to make. Do not let someone else's ideas run your paper.
It is generally better to paraphrase than to quote. Quotations tend to stick out. They draw attention to themselves and away from your ideas, so keep them to a minimum, and keep them short. If you can quote a few words or a phrase instead of an entire sentence, do it. Of course, you should do some quoting.
There are three reasons why you might prefer quotation over paraphrase for a piece of source material:
You might think these three qualities could pertain to most borrowed material, but in practice how often is a statement so authoritative that paraphrasing it would cause it to be less persuasive? How many sentences would lose something important if they were rephrased? How often is a statement so vivid that its vividness would be lost if rephrased? Not often. Most material can and should be paraphrased, but there are instances in which the original carries a weight that paraphrasing cannot capture. Those are the times when you should quote. A paper without any direct quotations would seem remiss.
For rare long quotes that are four lines of text or longer, use block quote format:
Here is an example of a block quote.
Whether paraphrasing or quoting, remember to cite. Also remember to introduce sources. The first time you use a source in a paper, it can be helpful to the reader if you identify the source (and not just in parenthetical citation). In some cases the source that should be identified is someone other than the author. In the example below, the expert is not the author but the person about whom the author is writing:
To introduce the author in this case would miss the point:
There is an important distinction here. If the writer is merely a journalist or a reporter, introducing the writer is optional. But if the writer is an expert (an author of an academic article, an expert who has a website, a book author who has mastered a particular topic, etc.), you should introduce the author by full name (and perhaps occupation or area of expertise) on first mention. After that, last name only or parenthetical citation is sufficient.