I also ski in a thin sock. Good or bad I'm skiing in Thorlos:http://dallas.thorlo.com/ws5/index.p...ctivity_id=2#A
I happen to believe that enabling good blood circulation to your feet is a key to keeping them warm. (I also liked Kazooski's comments about keeping your feet dry, too.) A few ideas to help enable good blood circulation to your feet...
* Get ski boots that have been properly fitted to your feet by an expert ski boot fitter. By having your ski boots properly fitted to your feet, your boots won't pinch your feet or lower leg anywhere and potentially cut off your circulation.
A boot fitter is someone who fits ski boots to skiers feet. Not all boots fit all skiers the same. Some boots fit skiers with wide feet better than others, other boots work better for people with big calve muscles, etc. Its very common for a boot fitter to modify a ski boot to help it to fit your feet (and lower leg) properly.
* When my feet start to get cold on the ski slopes, the first thing I do is to check how tight my ski boot buckles are. If after loosen my boot buckles I find myself sliding around in my boots while I"m skiing, then that tells me that I'm not skiing with very good technique. With proper fitting boots and good skiing technique, you should never have to over tighten up your boot's buckles to keep your feet from sliding around inside your boots while you are skiing.
It may not make sense at first, but you should never have to tighten up your ski boot buckles to the point that you have poor blood circulation to your feet.
* Last thoughts on improving blood circulation to your feet: It may help to undo your two lower boot buckles while you are riding on a chair lift. Also, if the chair lift has a foot rest, then using that might help, too.