This:
and/or this:

^ no fog clip for balaclavas
I haven't tried either one yet but the idea is to make sure that your breath doesn't get inside your goggles. There are more extravagant balaclava designs for diverting your breath downward but I think the first one might be good enough for me. My current balaclava has holes to exhale through but some of my breath still gets into my goggles from the lower vents. It hasn't been too much of a problem as long as I don't sit in one spot for too long.
Look to snowmobiling sites for various options.