If you do it all the time, you'll find out what works and what doesn't. A good wool touk and 800-1000 grain boots are a start with a couple layers of wool socks. Make sure you don't sweat while hking to your stand either. Also, when I drive to my stand, I have my heater turned off and the window down. The first hour is usually the toughest but it takes about that long for your body to acclimate to the cold.
If thats all your dealing with is 20f temps, your dreessing totally wrong.

Bobby