I learned long ago with other bikes: there are neighborhoods that you just don't ride through. They're the same ones you wouldn't walk through at night. In places like that there's always screws, nails, glass, sharp rusty metal, and various pointed whatnot just laying in the street waiting for a tire to get stuck in. The streetsweepers never go there because it's too shady. If there's any significant amount of trash on a street, I won't ride there. Haven't had any flats since I began this policy.