To defog your ski goggles, you shall have a check and make sure no snow is inside the goggles before you put them on. In case your ski goggles get fog, you shall prepare a tissue or small piece of cloth in your pocket and use it to wipe away moisture in the goggles.
Fog in ski goggles can be quite a pain in the neck. I love skiing and my exclusive tips are that before they are fogging, you need to carry a tissue or piece of cloth to wipe off the moisture on the screen. You have to make sure that air can circulate through your goggle to refrain from fogging.