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

Guard against inadvertent plagiarism
Engaging sources
Part I. Research and writing: from planning to production

Sloppy note-taking has caused grief for students and professionals alike, ranging from ridicule for trivial errors to professional exile for inadvertent plagiarism. To avoid that risk, commit to heart these two iron rules for recording information in notes:

Always unambiguously identify words and ideas from a source so that weeks or months later you cannot possibly mistake them for your own. As recommended above, record quotations and paraphrases with quotation marks, as well as in a font that unambiguously distinguishes them from your own ideas.

Never paraphrase a source so closely that a reader can match the phrasing and sense of your words with those in your source (see 7.9.2).

In fact, rather than retyping quotations of more than a few lines, download or photocopy them. Add to the top of the downloaded or photocopied page the name of the source and keywords for sorting.

This is important: never assume that you can use what you find online without citing its source, even if it's free and publicly available. Nothing releases you from the duty to acknowledge your use of anything you did not personally create yourself. (For more on plagiarism, see 7.9.)