It's generally pretty easy. Take it off the car and shake it - if it rattles, it's good, if it doesn't, clean it with brake parts cleaner unitl it does rattle, or replace it [they're only a few dollars]. One thing I also recommend replacing is the hoses [both upper and lower] that attach to the PCV valve, especially if they've never been replaced before. These hoses probably not only are brittle, but caked to hell on the inside with crusty oil residue, reducing the inside diameter. I'm actually doing this today, along with many other things to try to get my car to pass emissions.
Dax, i have it on good authority that just becuase the part rattles does not mean that it is okay, that just means it's not clogged. Honestly, for the price, and ease of change, to replace it is good peace of mind.