Do you soak it in sanitizer? Boil it? Do nothing?
I saw one on Amazon last week for like $30 and I figured what the heck, pick it up and I'll try it out, but now I'm not sure how I'd go about doing that.
Basically you can clean the parts just like anything else with a sterilizing solution. In order to clean the filter run the sterilizing solution through the system, or just soak it in the sterilizing agent. Be sure to flush with plenty of water before filtering your beer to get rid of the sterilizer. This site claims to use a bleach and water solution to sterilize and to store the filter:
Just back flush the filter at a low PSI (6-8) with sanitizing solution. If you're looking for recommendations, I'm a fan of Iodophor. It's a no-rinse sanitizing solution (unlike bleach) that doesn't impart any off flavors when mixed properly. Only downside to it is that it will give an orange tint to most things it touches. You can store the filter in the refrigerator to minimize bacterial exposure/growth.