Collecting and Observing Earthworms You'll find earthworms in garden soil, vacant lots, lawns, parks, or pastures. A cool, moist fall day or evening is a great time to look for worms. Humid days before rains, or during rain showers are especially good for collecting worms. Fall is the best time to sample worms because most are sexually mature, which helps you tell who's who.
Castings are signs that earthworms are present.
When you've found a likely spot for worms, dig a spadeful of soil and sort through it for earthworms. With experience, you may also find cocoons. Forest ecologist Cindy Hale gives directions for a method that will bring many of the deeper burrowing earthworms to the surface. Use string or boards to make boundaries around the area. Shake it up well.