Bottom line, you should cite any time you are giving ideas that are not your own.
Despite what you may think, it's perfectly fine to give an idea in a paper that isn't yours to help support your own thoughts/ideas or arguments. Just be sure to acknowledge who came up with the idea, and where you found the source by using an in-text citation and the complete source information in the bibliography.
In fact, professors like when you cite others' ideas because it shows that you put thought into your paper and you researched the topic thoroughly!
Citing sources and creating a Bibliography/Works Cited List:
There are three ways in which you can provide information from a source: paraphrasing, quoting or summarizing. All three of these methods require an in-text citation at the end of the statement:
Quoting: When you take a direct line from any source (whether it's a book, article, song and so on) you are quoting.
Paraphrasing: When you are taking something from a source and putting it in your own words to clarify a passage.
Summarizing: Like paraphrasing, you are taking something from a source and putting it in your own words, but in this case you are just going over the main points of the passage.
This short video from UCR offers some great ways to think about putting a source in your own words:
No matter what format you choose (summarizing, paraphrasing, or quoting), you should always to put an in-text citation within your text at the end of your quote/paraphrase/summary.
In the MLA format, it should include the author(s) last name, followed by the page numbers, in parenthesis at the end of your quote, paraphrase or summary (Smith 145-200).
If you mention the Smith in the beginning of the sentence, just include the page numbers where the source is found (145-200).\
As always, there are variations. If you're not sure, contact us or consult OWL Purdue page on in-text citations for your particular style.