Enter the paper or project into your computer. For larger projects where this is difficult, use a scanning program that translates scanned images into text documents.
Run a Google search of some of the titles, headings or topic sentences found in the work you are researching. If an exact match, or one very close to it, shows up somewhere in the search results, the work might have been plagiarized.
Compare the writing that you are checking against other samples of writing you have from that writer. Look for phrasings that don't make sense and styles that are vastly different from other samples. These are signs of possible plagiarism.
Scan the references list carefully to look for signs of plagiarism. Check for references that are way out of date or that don't seem to align with the content in the paper.
Run a portion of the work through an online plagiarism checker. Plagium is a tool that is free to use that lets you know if copy has been plagiarized. Try Copyscape for another perspective, but to get more than a few results you have to pay for the service.