Good stuff already mentioned.

A couple of mistakes I have made that I suggest you avoid. For sure make certain that your boot is large enough to accomadate your foot size + a thick sock. Boots that aretoo tight will restrict blood flow and this will make the "cold foot" syndrome even worse. I have packed my foot and multiple pairs of "hunting socks" into my hunting boot only to sit miserable all day because I had more or less cut the blood flow to my toes to a minimum !!! The right fit and one good pair of insulated sock is enough. Another mistake is to buy a good isnulated boot then put your foot into a pair of"hunting socks" that are 50% or more cotton. Been there and done that too.Cotton blends areOK for moderate weather but not when it is near freezing and certainly not down in or below the teens.Buy a sock that is well made, high in wool fiber and wicking man made fibers .... and no cotton! None of these are cheap, but it is $10-$15 well spent !!! Try adding a thin Thisulate "sock liner". These are relatively inexpensive and are designed to move sweat away from your foot quiclkly and efficiently.

If none of this works for you, try an "over boot". These are rather bulky, and essentially a "sleeping bag" for feet. Theyare super warm, especially when a couple of "Hot Hands" are tossed into each. My uncle, who was still hunting well into his80's used these. He swore by them. I may try them in 20 or more years ...certainly hope to do so.