There are some commerically available anti-fogging spray, you can have a try .Don't dress too much when skiing in case your body get warmer and the temperature difference between the outside air and your skin will be greater and cause condensation . Put on your goggles before you go outside and don't put on them until you finish the skiing .
Keep the air vents on your ski goggles free and unobstructed. Every so often check the top of your goggles to clear off any snow that may have accumulated and may be blocking the vents. Air flow keeps fog away.