Theme is such a huge concept and is vitally important to teach to students. I pinned this idea that I thought was brilliant in its simplicity.
(Image credit: http://theopendoorclassroom.blogspot.ca/2012/02/teaching-theme-of-books.html)
Teaching diploma exam level courses here in Alberta, where students are expected to write a critical/analytic response to a text based on a specific prompt that they have not seen before, we try to look at every possible theme that a student can pull and write about from a given text. I can imagine keeping a list like the one that Erin has created for her Elementary students on her blog The Open Door Classroom. I could add themes or topics in the left hand column, have students discuss and create an explanation as to why this would be an important theme or topic to explore, and keep a tally of texts discussed in relation to this theme or topic in the final column. This could be a great tool for diploma examination prep (or, in your case, final exam prep, essay prep, etc.).
What I like most about this strategy is that its simplicity means that this can be easily adapted to any classroom. While Erin originally created this chart for very young students, I immediately thought about how I would use it in a grade 12 classroom. I imagine that this could also be used in other subject areas- Social Studies to keep track of major philosophies discussed, Mathematics to discuss formulas used for particular purposes, etc.
Food for thought... what would you use a chart like this for? What adaptations would you make?