Promoting Integrity in Assignments:
Assign Unpublished or Recently Published Materials
If students are asked to respond to something that has been recently published, it is less likely that they will be able to find material to plagiarize on the topic.
Because I am an avid reader, I often come across articles that are relevant to the classes I teach; articles such as those published in The Chronicle of Higher Education, Inside Higher Ed, or some other source that was published within a couple of days of my using it in class. Even when there is much written on the topic, by asking students to respond to a specific article or to incorporate it into their paper or project, you cut down on the possibility of plagiarism.
In a similar vein, asking that certain sources or types of sources be specifically included in an assignment can help eliminate plagiarism.