The trick is to not get cold in the first place. Don't build up a sweat by walking to your hunt location with all your cold weather gear on. All that sweat is just going to sap the warmth right out of your body. I usually carry a small rucksack with my cold weather gear stuffed in it and not put it on until I'm acutally where I plan on hunting. The walk out there might be cold but you can at least walk faster to keep warm. You can't keep warm by doing that on stand.

Another idea I picked up is to buy an old cheap (but warm) sleeping bag. Cut out holes for your arms to slip in and out of and use suspenders to keep it up and wear it while out on stand. You probably won't get it to seal out all cold but it will keep your torso warm and toasty. Think of it as a big mitten for your whole body. The tough part is finding a tall enough sleeping bag that also has a camo pattern. I just wrapped mine in camo burlap with a few stiches to hold it on and found that it really works very well at hiding my outline.