As was mentioned on the "Avoiding Plagiarism" main page, avoiding plagiarism is as simple--and as difficult--as acknowledging when information came from another source. There are several ways to make clear who the author is of borrowed information, depending on the type of assignment.
Research assignments, where you use multiple sources to support your ideas/arguments about a topic, will use a citation method such as APA or MLA, and you will usually start the sentences which use someone else's ideas with a signal phrase.
Example: According to John Smith's study, 3 of 4 students reported not having enough time to do their assignments (2018, p. 23).
See the "Integrating Sources Ethically" page on this guide for more information as well as specific techniques for avoiding plagiarism in this type of assignment.
Critical/analytical review assignments, where you have one source that you are analyzing and commenting on, will typically only need the use of the author's name in the sentence/section.
Example: John Smith argues in his article, "Why Students Procrastinate," that most students procrastinate because they are just lazy. However, this argument is not convincing because Smith does not provide any data to back up his conclusion.
Since it can be difficult to find the mistakes and unclear spots in our own work, try to have someone else read your assignment/paper for you--and ask your reader to identify what parts were written by you and where you used other people's words/ideas. If your reader has trouble doing that, you should look at revising your work--and possibly contacting the Learning Center, the librarians, and/or your professor for help.