Naiya made a thread in the Attaining Lucidity forum about lucid dreaming in general and DILDs and WILDs. In the post she mentions how to reality check and, after thinking about it, it really does make sense.

To put it in a simple words as possible: Just pretend that you're already in a dream when you RC and prove that you're not by trying to use an ability or by trying to remember how you got to where you are. Then do a nose pinch or look at your hands.