It took me a while to get a good system going to keep my goggles clear... First, I try to manage my general heat generation, it's important for survival in the winter anyway, so if I find I'm getting warm, I try to unzip something right away or take it easier to regulate my heat. I've also chosen goggles that have lots of venting at the top edge, making sure that neither my balaclava, nor hat, nor helmet is covering those vents... For the most part, it's worked. There are times when I'm going up hill or making a big effort in deep snow that I just can't regulate my body heat enough and my goggles fog or frost over (it was pretty darn cold this winter!), they usually clear out as my body heat returns to normal of I get some speed up... Hope that helps! Oh, and this isn't a product plug, they just work for me, but I have Spy brand goggles...