Plagiarism is an increasing problem in high schools and universities. To address the issue of how to teach students not to plagiarize, this study examined several pedagogical approaches for reducing plagiarism and the use of Turnitin, an online plagiarism detection software. The study found a significant difference between the control group and one instructional treatment group that was reflected in the reduced level of plagiarized text. This finding indicates that the lack of knowledge in proper documentation and paraphrasing is a primary reason why some students plagiarize, albeit perhaps inadvertently. Implications point to the need for consistent in-depth instruction in proper quotation, citation, and paraphrasing techniques. (Contains 3 tables and 1 figure.)