If you've been vermicomposting for a few months or a several years, it's likely that you've discovered separating the worms from their castings a time consuming process, if you attempt to do it by hand.
The video below offers a cheap and easy solution you can implement for you home vermicomposting efforts. I spent 99 cents on this harvester. (I told you it was cheap.)
Worms will move away from light, so a few minutes before you plan to harvest worms or castings, simply expose the top layer of your bin to light. The worms will move down away from the light and you can scrape the top layer of castings up with the kitty litter scoop.
Keep going until you are left with mostly worms in the bottom of your bin.