I'm sure this is way late, but you can always take a lesson from scuba divers…spit on the inside of your googles, then smear it around a little bit. Not the nicest way, but as long as it works…Another helpful tip is to get some shaving cream foam, put a little on the inside of your goggles, then rub it in using a towel or cloth until it completely disappears (it may take a few minutes, but dont worry it'll go away after a while). That should prevent fog ups for a few days at least. Just try not to get any on the padding, that could create a mess.
The best things to do are to keep the goggles clean, dry, and lenses scratch free. I always store my goggles in a cloth bag or something until ready to wear them. If it is snowing, do not put them up on your head. Also, make sure the vents are open and clear away from your hat or helmet.