i think the biggest factor in this is boot fit. if your boots are too large or small, you will get cold feet. always make sure to buy them exactly the right size.
also, try to wear thick socks, but not extra thick because they will begin in cut off circulation and inhibit your foots ability to heat the boot.
my biggest weapon in the fight against cold feet is at the beginning of every other season, i buy a box of 50 footwarmers, and use them as both foot and hand warmers. its only about $40 a box (check ebay) and personally, i only find it cold enough to use them about 25 days of the season, so they can sometimes last a season and a half or two seasons. they are also great to have for filming, the adhesive ones when added to a camera battery pack can help make it last longer in the cold.