Find the anterior or head end, which is more pointed and narrow. You can also place the worm on a rough piece of paper and see which direction it travels. The head end usually goes forward first. This number is different in different species, so counting segments can help you know whether your worms are of different species. Look for the hair-like bristles called setae around or under the worm's body.
Worms use their setae to help crawl and also to grip and anchor themselves firmly in the ground.
Look at the worm's shape. Try turning the worm. A worm turned over will immediately right itself. Pigmented worm species live at or near the surface of the soil in organic matter such as leaf litter or compost piles, but they may also burrow very deeply and feed at the surface on fresh litter. Nonpigmented worms live and feed in the soil, not at the surface.