first thing is to make sure you're wearing thin socks. alot of people think they need thick socks to keep warm but they just cut off the circulation to your foot. smartwool phd ski/snowboard socks are pretty much the shit. they make a couple of different thicknesses - all are acceptable.
next thing to do is ditch the stock insole from your boot and get an aftermarket footbed with more support: Sole, Remind, Superfeet, etc.
are you really cranking down the laces? i actually find that snug but slightly loosened boots are best for me....