University of Wisconsin System guidelines forbid plagiarism, which is a form of academic misconduct and an intellectual crime. Among those forms of plagiarism forbidden:
As a general rule, three or more consecutive words from another author that you include in your own work must appear in quotation marks and the page on which they originally appeared must be provided, generally in parentheses at the end of your sentence. If the author you're using as a source uses a word that you wouldn't ordinarily use - perhaps a coined phrase - that one word should appear in quotation marks in your paper, and the page on which it (first) appears in the original should be included parenthetically at the end of your sentence and linked to your bibliography, if you are using MLA format.
Not putting directly quoted words in quotation marks constitutes the most obvious form of plagiarism, even though it might seem like it is merely a punctuation error. You may fall into this error if, when you are taking notes on a text, you inadvertantly forget to put direct quotes into quotation marks in your notes. Obviously you might then think that those were your own words when you read over your notes for preparing your papers. Inadvertant error or not, this constitutes plagiarism.
Even if you are not quoting directly from your source, if you are using another person's argument - if you are paraphrasing someone else's argument - you must give credit or you will be committing plagiarism! The easiest way to avoid this sort of plagiarism is, obviously, to give credit where credit is due. You might say, for instance, "According to Joe Schmoe, the American west was won using pie." If you are adopting someone else's argument but not that person's words, you also need to give inclusive page numbers where that argument was first formulated, linked to your bibliography, if you are using MLA format. It might look like this: "According to Joe Schmoe, the American west was won by pie" (13-36). If you simply assert that the American west was won by pie, you would be plagiarizing (unless you hadn't read Schmoe's argument at all: then we would have a very odd coincidence).Sometimes you will formulate your own argument and then discover that someone else makes the same argument. If you simply ignore what you read - if you pretend that you haven't actually read it - you make yourself liable to accusations of plagiarism, something you don't want to do. The easiest way to obviate this problem is to mention that whomever you've read makes much the same argument as you. It would be helpful, then, if you could identify ways that you go in another direction from that person in your argument, but that's not precisely a plagiarisim issue.
To avoid plagiarism, it is best to err on the side of citing too much rather than run the risk of inadequately citing. There's nothing wrong with using direct quotation; you're better off using it and citing your source than inadvertantly plagiarizing, using someone else's language. Likewise, there's nothing wrong with including someone else's argument, as long as you make sure to say whose argument it is and provide information are where that person makes that argument. There's also nothing wrong with acknowledging that a professional made the same argument about something that you want to make: doesn't it class you with the professional? Nonetheless, you will want to go on to use that argument to your own ends.
Multiple cases may lead to expulsion from the university. Don't do it!