A basic requirement to avoid plagiarism is to properly cite your sources. Using a citation management tool like RefWorks, Zotero or Mendeley can help you track them.
Keep detailed notes as you read content. If you make a note and it is word-for-word, use quotation marks and note the resource and page number where you found it.
Do not cut and paste content into your papers.
Keep your writing separate from your sources and from your notes to help decrease the risk of accidental plagiarism.
Finally, research and writing is a time-consuming process so planning ahead is critical. Allow enough time to read, take notes, think about how to use the information you find, and properly cite the sources.
For more information, refer to the Turnitin Policy and Plagiarism Overview guidelines in the Saybrook Center for Writing and Academic Success.