"Why do I have to cite my sources?"
When you do research, you work with other people's ideas as well as your own. This is an integral part of research, to combine your ideas with the ideas of others and create something new. It is very important that you give credit where credit is due, and this is one reason you need to cite your sources. If you don't, you're committing plagiarism, which is is both lying and stealing. When you cite your sources, you tell your readers about where you found some of the inspiration for your work, and you credit those who inspired you, or those whose work you used. Also, when you cite your sources, you help your readers find those sources if they wish to read more about the ideas presented in your work.
"How do I decide when to cite a source?"
Whenever you use information from articles, books, interviews, etc., you must credit the authors of those works by citing the sources. When the information you're using is your own idea, or when the information is common knowledge (for example, that Thomas Jefferson was president of the United States), then you do not need to cite.
"What if I take the information and reword it?"
Rewording something is called "paraphrasing." If you paraphrase, you still have to cite your source, because the ideas you are using belong to another person.
"So what do I do if I paraphrase?"
When you're going to paraphrase, introduce this in a way that makes it clear the ideas belong to someone else. For example, you could say, "Peterson argues that...," or "In her book, the author mentions several times that...." Be sure to add page numbers at the end of your citation, and be sure to include a citation in your Works Cited page.
How might you format your in-text citations so that they're more compliant with MLA guidelines?
You already know why MLA formatting guidelines are an important part of an academic paper, but let’s face it—who can remember all those rules about when and where certain citation information is requisite and when and where particular punctuation is appropriate? Thankfully, memorizing all of MLA’s formatting guidelines is not necessary! MLA style guides can be found easily online or in texts like The MLA Handbook, and writers can refer to these resources when they are unclear about a particular MLA style guideline.
Nonetheless, as you create multiple drafts of your composition papers, there are some MLA conventions that you will need to call on time and time again. In particular, as you integrate source material masterfully into your work, you will be required to call on proper in-text citation guidelines repeatedly. It is therefore important that you take the time to memorize the MLA guidelines for in-text citations.
Because the use of in-text citations will be so integral to your writing processes, being able to instantly craft correct citations and identify incorrect citations will save you time during writing and will help you avoid having unnecessary points taken off for citation errors.
Here is the standard correct in-text citation style according to MLA guidelines:
“Quotation” (Author's Last Name Page Number).
Take a moment to carefully consider the placement of the parts and punctuation of this in-text citation. Note that there is no punctuation indicating the end of a sentence inside of the quotation marks—closing punctuation should instead follow the parentheses. There is also no punctuation between the author’s last name and the page number inside of the parentheses. The misplacement of these simple punctuation marks is one of the most common errors students make when crafting in-text citations.
So, let's say we have the following quote, which comes from page 100 of Elizabeth Gaskell's North and South: "Margaret had never spoken of Helstone since she left it." 
The following examples show incorrect MLA formatting:
"Margaret had never spoken of Helstone since she left it." (Gaskell 100)
Incorrect because the period falls within the quotation marks
"Margaret had never spoken of Helstone since she left it" (Gaskell, 100).
Incorrect because of the comma separating the author's last name and the page number
"Margaret had never spoken of Helstone since she left it" (Elizabeth Gaskell 100).
Incorrect because the author's full name is used instead of just her last name
"Margaret had never spoken of Helstone since she left it" (North and South 100).
Incorrect because the title of the work appears, rather than the author's last name; the title should only be used if no author name is provided
The following example shows correct MLA formatting:
"Margaret had never spoken of Helstone since she left it" (Gaskell 100).
However, there are exceptions to the above citation guideline. Consider the following format of an in-text citation, which is also formed correctly.
Elizabeth Gaskell's narrator makes it clear that "Margaret had never spoken of Helstone since she left it" (100).
Do you notice the difference between this citation format and the format of the first example? Unlike the first example, this citation does not list the author’s last name inside the parentheses. This is because the last name is included in quotation's introduction, which makes the identity of the author clear to the reader. Including the author’s last name again inside of the parenthesis would be thus redundant and is not required for MLA citation.
The same rule about inclusion of the author’s last name applies for paraphrased information, as well, as shown in the following example:
Elizabeth Gaskell's narrator makes it clear that her protagonist does not speak of her home once she is in Milton (100).
In this paraphrase, the author’s last name precedes the paraphrased material, but as in the case of quotation integration, if the author’s last name is not described in the paraphrase then it is required inside of the parentheses before the page number.
Being more compliant with MLA in-text citation guidelines will become easier if you review these examples and the citation rules on which they rely.
 Gaskell, Elizabeth. North and South. Oxford: Oxford UP, 1973. Print.
Exercise: Formatting In-text Citations in MLA Style
"Formatting In-text Citations" was written by Jennifer Yirinec and Lauren Cutlip