I have found that any variable besides "x" in my physics class just sets my students' heads spinning. And when you throw in a Greek letter, they get even more confused; they hardly know what you're drawing, let alone what you're saying. So, to alleviate this little problem, I made a big poster to print on our plotter and hang in my room. Now, when I introduce a Greek letter (like "mu" for the coefficient of friction or "lambda" for wavelength), I just point to the poster and they understand. I think just seeing the Greek alphabet laid out before them and having it always on hand helps. I recommend this poster for anyone who uses Greek letters in their classroom, as it has proven useful to me and several of my colleagues whom I have printed some for.
Please note, this is a large poster and is intended to be printed using a plotter.