Study the foundations. For each phase of teaching the elements of graphic novels, there's at least one good example. The Eisner awards often feature some of the best graphic novels in a wide range of categories, including writing (see Resources below).
Find a class to teach. Some colleges offer popular culture courses, but they can be difficult to get into. Your best bet is probably to start your own series of seminars. You might find the local comics shop willing to host, but the patrons may not be open to learning more. See if you can open up something at your local library.
Acquire teaching materials. While this does mean that you need traditional materials, you'll also need a textbook or two dealing with the materials. Both Will Eisner and Scott McCloud have written well-regarded texts on the writing of graphic novels (see Resources below).
Discuss with your class those elements that stand out in graphic novels. Most are familiar with the hyperbole and grand standing of super heroes, but that only underscores the importance of genre, and dialogue is a central element to most graphic novels.
Show the importance of lettering in graphic novel, the combination of art and writing to get the message across.
Generate a fun atmosphere with free dialogue. Graphic novels offer rare interaction between art types and possibilities for expression. Don't stifle that.