I agree with the windbreaker and layering to stay warm....Personally my cold points are legs, hands, and ears.....If I ride when it is cold I typically wear 2 pairs of pants (obviously the outer one being somewhat larger so as not to be tight when put over my "regular" pants)....I typically wear 2 pairs of pants instead of long johns and a pair of pants so if I decide to shop or be inside for a prolonged period of time I can simply remove the outer covering and go about my business....not so easy to do with the long john pants combo!
Andrew