I wear plastic shopping bags over sneakers, wind pants, a good outer shell jacket with a sweater and a fleece layer underneath, and some mitt gloves. If snowing, ski goggles are invaluable as snow in the eye hurts, especially at speed. For really cold weather, I'll also wear a scarf, and a winter hat under my hood. This setup will has me overheating at -4oF so I'd imagine it's probably good to even lower.

In short, wind-proof outer layer, goggles, and minimizing exposed skin will go a long way to staying warm.