Wear a warm hat. Seriously. Without blood flow to your feet, NOTHING you wear will keep your feet warm. It's all about blood flow. Heat up your brain's thermostat and in an effort too cool itself your brain will command your blood vessels to expand and pump warm blood away from the brain and to your extremities.

Next in importance - your core. Keep your core temp up by abiding by the "ABC Rule" (Anything But Cotton). Fleece, wool, nylon, polyester etc. Then add a windbreaker and your feet will go to Miami Beach! (Unless your shoes are too tight! Blood flow baby, blood flow!...)