Was "winter" camping a couple weekends back, and was struggling with staying warm. I think that part of the problem was that I had my fleece in with me as a pillow, and that my face was inside the bag. Any suggestions - how do the more experienced among us arrange themselves for a good night's sleep in a mummy bag?

Steadman, were you in a tent, hammock, out under the stars? Was there weather? What was the lowest temp you encountered?

In general, a hat makes a huge difference in staying warm and I start there. Either a fleece bomber hat or a thick knit watch cap, pulled down over my ears. Socks on the tootsies, and hands. Something rolled up is my pillow and typically is outside the bag, but I've done both. Fleece or wool underwear helps. Sometimes I'll unzip the bag and use it as a quilt, keeping the entire thing on top of me to make use of all the insulation that would normally get crushed under me.
Here,(texas) it gets into the 20'sF, I don't have much experience colder than that. Some of the snow monsters on this site might have other advice.

Almost everytime I have been cold in the backcountry the problem was too little insulation on the bottom.

The second problem is a hat or balaclava.

The third problem is I did not eat right.

The fourth problem is I over extended myself physically during the day.

I have not used a mummy bag in so long I am not competent to answer.

If it's cold and I'm in the bag yes, pillow outside. (often
I sleep with the bag unzipped, quilt style)

1) try to keep your face out of the bag so your wet breath doesn't dampen your bag. a balaclava/face mask really helps for this - think bank robber style - although I don't use this till it's really cold

2) a good toque (fleece hat) I always sleep in one

3) eat something before you go to bed. God gave us chocolate
and cookies because she loves us and wants us to be happy in sleeping bags.

4) dry base layer and dry socks. (sometimes more, I often sleep
in a fleece)

Thank you... that helps a lot.

Temps were right around freezing. I was wearing a hat, long johns, and dry socks. In a Rainshadow 2 tent.

Biggest problem was the insulation under the bag (uninsulated airmatress). I'd done this before, but I did not have a blanket between me and the airmatress, and I was using a down vice synthetic bag.

However, I was feeling damp towards morning after huddling down in the bag and thought (after reading this forum) that my posture in the bag had something to do with it - besides, if my face is plugging the hole in the bag, there can't be any drafts, right?

I'll try it with my pillow outside the bag next time and my face in the hole.

Ditch the uninsulated and get something insulated. The exception to this would be the NeoAir, which is uninsulated but manages to keep cold blooded me warm to below freezing each time. Been down to 20F with it.

A big agnes insulted air core, exped syn or downmat, neoair, or perhaps even a Kooka Bay - or add a ccf foam pad to your kit and put it on top of the uninsulated pad.

Bingo. There's your problem....ditch the air mattress and get either a foam pad or Thermorest. You'll be a happy camper.

I started out with the ccf pad under the airmatress (last time I did ccf pad/matress/poncho liner/sleeping bag; this time I left the poncho liner at home) and then put the ccf pad on top of the matress - which was better. Think that if I'm going to make this work for a "winter in Virginia" scenario, I need to bring the poncho liner as well or invest in a better pad.

Real issue that I wanted to talk about was pillow placement, though. I think I was also running into draft/moisture issues inside the bag and that this was also making me cold.

If I'm reading your initial post right, your face (specifically your mouth and nose) was actually inside the bag? If so, your breathing was putting a lot of moisture into the bag.

If it's cold enough that I want the hood around my head, I want my pillow under the bag, and my mouth and nose outside the bag. I usually snug the hood around my face fairly tight. If having my eyes, nose, and mouth exposed lets them get cold, I wear a balaclava, pulled over my mouth and nose (which is how I learned how much moisture is in breath: the first time I did this, the balaclava was pretty wet.) I'm also a side sleeper; to avoid having my face in the side of the hood, I roll the bag with me, so my face stays in the "hole."

If I don't need the hood around my head, it's usually warm enough that I can unzip the bag and use it as a quilt (with, maybe, a stocking cap on.)

The only other thing I can think of that would affect moisture is if you were zipping the bag up and getting too warm, with the resulting sweat causing issues. Given your experience, I'd have a hard time believing you'd do that.

Oh yeah.. big time.. ditto on the bingo. You might as well be hanging in a hammock with no underquilt.. you quite literally freeze your butt off..

Even adding a lightweight blue foam pad to the top of your uninsulated air mattress will help you a lot.

In thirty below zero weather here I use a thermarest between two blue foam pads top and bottom.

At the temps you describe even a regular thermarest (or downmat, or big agnes aircore, or zrest, etc. etc.) will make you a lot warmer..

I do not have near the experience as many avid backpackers here. I do however agree wholeheartedly. On my trip last April I was in A shelter on top Mt Leconte. I was just gettingback to backpacking. I used my thirty year old snow lion synthetic bag. It dropped to 7 degrees F. that night with 3o mile an hour winds. I wore my long johns my fleece and hat to bed. The thing I am conviced saved me was my Thermarest prolight. I bought it before I left and glad i did. Several times in the night my feet slipped off the pad and once a leg. I knew it quick as they got cold but warmed right up when I shifted back on it. I know alot of folks use short pads to save weight, But after that night I will carry a few ounces more and take my full length pad! Cold comes from below, and fast!

Yes get a warmer pad. That will make a huge difference. Another thing you might want to try is an open face balaclava. I find that a lot of my perception of temp is in the back of my neck and head. If I keep that area warm, I feel warm. If that area is cold or drafty I'll feel cold even when I'm otherwise warmly enough dressed.

Thank you. I'll get my face (and pillow) out of the bag, and get more insulation under me...