I try to avoid assignments where students are allowed to choose their own focus. Leaving an assignment completely open-ended tends to make plagiarism too tempting to resist. Besides, I'd rather not spend my time frantically searching Sparknotes for evidence to "bust" students for plagiarism. For me, a better solution is to require unusual synthesis between texts, or to require inclusion of a personal connection with the material. It has also worked well in the past to require students to find an existing piece of criticism on the text we're working on, and then to have them agree or disagree with its content. One final possibility I've tried is to require students to respond in writing to an issue touched on in a class discussion, or on one of our online discussion forums. (Still, though, this focus is often not unique and specific enough to make plagiarism impossible.)
