Here's how I went about harvesting worm castings for the first time. I scooped up what looked to be ripe soil in a "finished" corner of my worm box and put it in a bucket. I then dumped it out on a tarp to form a little mountain. I left it out in the sun for a half hour. The worms headed for the coolest region—straight down—and I scraped worm castings off of the top. By the time I had made it to the bottom—yes, I know, this is not exactly Everest, but I was working slowly and carefully on this first test run—a whole mass of worms was down there, so I collected them and put them back into the bin.