Oil your chain often. If you get out and get too cold to ride or the weather changes for the worst, do not hesitate to call for a ride. Its OK in the winter to do alternative activities, we even encourage it. Running, swimming, XC skiing, hill running, snowshoeing, running up stairs can all provide a beneficial aerobic and endurance enhancing workout. If cross training is done with the same intensity and similar durations as your cycling activities, cross training will help you get ready for the upcoming season.
Winter weather can also provide some good opportunities to get into the weight room.