I've done alot of winter camping to include sub-zero temps and really have nothing to add to what has already been posted in terms of layers and materials. For me:
- Synthetic, wicking base layer, thickness dependent upon temps and activity
- (2) pair merino wool socks, hand warmers on top of foot between sock layers if standing around
- Winter weight USGI surplus wool pants and shirt
- Windbreaking outer shell jacket
- USGI wool glove liners. Bring multiple pair since if one pair gets wet, simply swap them out. If needed, hand warmers on top of hand (don't put them on the palm of your hand)
- Muff or chops depending on what I'm doing
- Balaclava mostly around my neck but can be pulled over my head if I get cold
If your hands/feet get cold, it's painfully miserable so I pay alot of attention to those. My core has several layers that can be opened, removed or added so I don't sweat and pay particular attention to your neck. By wearing some form of gaiter or balaclava around your neck, you'll preserve your core heat while allowing for less core layers which translates to less sweat.
I'll usually just wear a ballcap if moving since I let my head radiate excess heat when working. Once still for awhile, I'll put a beanie or balaclava over the hat.