A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Know when to summarize, paraphrase, or quote
Engaging sources
Part I. Research and writing: from planning to production

It would take you forever to transcribe the exact words of every source you might want to use, so you must know when not to quote, but to summarize or paraphrase.

Summarize when you need only the general point of a passage, section, or even whole article or book. Summary is useful for general context or related but not specifically relevant data or views. A summary of a source never serves as good evidence (see 5.4.2 for more on evidence).

Paraphrase when you can represent what a source says more clearly or pointedly than it does. Paraphrase doesn't mean just changing a word or two. You must use your own words and your own phrasing to replace most of the words and phrasing of the passage (see 7.9.2). A paraphrase is never as good evidence as a direct quotation.

Record exact quotations when they serve these purposes:

The quoted words constitute evidence that backs up your reasons. If, for example, you wanted to claim that different regions responded to the Battle of the Alamo differently, you would quote exact words from different newspapers. You would paraphrase them if you needed only their general sentiments.

The words are from an authority who backs up your view.

They are strikingly original.

They express your ideas so compellingly that the quotation can frame the rest of your discussion.

They state a view that you disagree with, and to be fair you want to state that view exactly.

If you don't record important words now, you can't quote them later. So copy or photocopy passages more often than you think you'll need (for more on photocopying, see 4.3.1). Never abbreviate a quotation thinking you can accurately reconstruct it later. You can't. If you misquote, you fatally undermine your credibility, so double check your quote against the original. Then check it again.