A couple things.
Heat mold, and custom insoles.
If you get pain in the arch area I would say you need more arch support. Also you may be over tightening your ankle strap. Make sure the boots you buy fit properly in your bindings, esp in the heel cup. if you have lots-o-slop in the heel cup area you'll have to crank the bindings down super tight, thus forcing the curvature of you arch down and possibly causing pressure points in other areas, all leading to pain.