A good chunk of this has been covered above I think, but this is how I approach cold weather camping.

A big thing I've found in winter is to have a tent with solid walls (i.e., not mesh). I have slept in tents with partial mesh walls and I found I really felt even a small breeze as it goes through the tent.

Between me & the ground (bottom up) I typically use:

• Reflective layer (like an All Weather emergency blanket, shiny side up) to bounce some of my lost heat back to me
• Closed cell foam (I've recently combined this and the previous component into a single piece of gear with a Therm-A-Rest Ridgerest Solite that has a reflective side)
• Self-inflating pad (I us a 3.8 cm thick pad, MEC brand)

For a sleeping bag I use a -7 C (20 F) down bag and will also use a synthetic overbag that is rated for +15 C (60 F) on its own which adds 5 to 10 C (9 to 18 F) to the system. In addition to adding warmth, the condensation forms on the outer synthetic bag keeping the inner down bag dry. I also usually cinch things up so only my nose/mouth area is visible.

For clothing, I'll usually just do a dry pair of socks & a base layer. I won't necessarily wear a toque or anything on my head due to how I cover up with the sleeping bag.

Filling a Naglene with hot water & bringing that to bed with you is good too ... it also makes sure you have liquid water when you wake up! As an aside, if you have other bottles, store them upside down so that if they start to freeze, the unfrozen water will still be accessible.

Also, have a good high calorie snack before bed. I usually bring chocolate bars for this (Snickers, preferably ).

When I have found myself out with a bag that wasn't warm enough for the weather, layering up with whatever could provide warmth (like fleece mid-layers) helps. I used my camp blanket in my bag with me once too (not a winter camp, but I unwisely had my summer bag with me) but I found it was hard to keep in place. I also once used a puffy down jacket around my sleeping bag, partially zipping it, which provided some extra warmth.