So you just bought a pair of really awesome goggles, they might have been a pair of Oakley's or Smith's that are close to 200 bucks with a photochromatic or polarized lens or maybe you went huge and got the Airwave or Recon with GPS and all that jazz. No matter what kind of goggle you have they tend to get dirty and you want to be able to see through them. If you want to be able to continue seeing through your goggles you need to clean them properly.
If you're going to keep them clean you should store them properly. Most goggles come with a goggle bag, keep them stored in that.
For additional protection put your goggles in a hard case too. It's not necessary but it's really cool if you like accesories.
To clean your goggles you don't have to buy anything special just use the goggle bag that your goggles came with. DO NOT use paper towels, your sweatshirt or even that blanket you've had since you were a baby. Just use the goggle bag gently wiping away dust and finger prints on the outside lens.
Cleaning the inside/interior lens is a bit harder. All the manufacterers put an anti-fog coating on the interior lens and it's important that we keep that layer of anti-fog treatment on the lens where it belongs. In order to do that it's best to just leave that part of the goggle alone if you can. Sometimes dust or hair might make it's way in there, if so just dab it with that trusty goggle bag, a little wiping is ok as long as the goggle is 100% dry. If there is moisture in there and you wipe the interior lens you will wipe away the anti-fog coating. That's not cool and now your awesome $200 goggles are fogging up all the time, just let them air dry before cleaning them and you'll stay stoked.
It's a really good idea to have multiple goggles not only for varying lighting conditions or if your buddy forgot his pair on the kitchen counter (usually me), but just in case you take a fall and get snow inside your goggle. To be able to just ski down grab your backup pair while the other pair drys out is really nice and will keep you happy and your goggles in good shape.