Layers...of different kinds for different body parts.

My basic system (which kicks in somewhere around 40F) involves a windproof/water resistant soft shell with pit zips and wool layers (shirts, sweaters, etc.) of various densities, layers of tights, layers of gloves, a face covering, and a snowboard helmet. What works for each person is a bit different (for example, I find that my hands run really hot compared to others.)

Hands, feet, and face will get colder on a bike than, say, walking or running. Good boots/socks and gloves/mittens/Bar Mitts are worth the investment. Eye protection makes life better. Something to break the wind on the legs is nice, but isn't really necessary until you start getting into the really cold weather (if you wanted to ride at 0F or something.)

Have fun guys...I'm out of Wisconsin and in North Carolina this winter, so don't have to deal with any of that