It's all experimentation, and I definitely don't have a system down yet. Some days, I get by with my REI riding pants over padded shorts. Sometimes I'll want tights under them. Sometimes I'll go back and put leg warmers on under them, and take them off. Sometimes it's so bad I wear a base layer under everything, with two long sleeve jerseys and a windbreaker. Sometimes, I have to squeeze in a hoodie, because I'm running out of jerseys. Sometimes I just grab a blanket, and sit on the porch and drink coffee and wish I was riding. I have found that expensive cycling winter gloves suck even worse than the seven dollar ski gloves at walgreens. If it's a long ride and I want the padding, I'll wear regular cycling gloves under them. I hate winter here. Stupid snow, stupid drivers, stupid layers of stupid clothes, and stupid balaclacavacacavas. Which I will NEVER be able to pronounce. Stupid girlfriend laughing at me when I say baclava.
I have taken to riding with one pannier so I always have a place to throw layers I remove, or stash extras. It's handy because sometimes the sun will drop behind a cloud, and the temperature will drop right out.
Winter sucks. I would like to try a looping self supported century here in Salt Lake one of these weekends, though. Just to see if I can do it without getting hit by a damn UPS truck.