Is the pattern that there is no pattern?

Monday, August 10, 2009 - Ran 4.50 miles at De Anza Cove today without any pain. I am getting really confused because I can't figure out any sort of pattern for things to do to avoid shin pain. Granted, I ran 80% of my run today on the grassy part of the boardwalk that follows the coast, but not only did I not have pain today, but I also 1) did not use Salonpas the night before 2) nor did I do any of my PT exercises or stretches and 3) I only used the stick for about 2-3 minutes the night prior when I usually spend 10+ minutes using the stick on my legs. Is the key to shin-splints-free running to run exclusively on soft surfaces (i.e, grass, dirt trails)? Or is inaction the real action to running without pain?