Go Hunting in the Rain
Rain storms bring out worms better than anything else. Before the cement dries and the worms fry, go out and pick worms off the sidewalk, pavement or even in the grass. You can store earthworms at home in a bucket filled with dirt if you don't plan on going fishing right after a rain storm.
Use Coffee Grounds
Dump used coffee grounds onto an open space of grass or dirt. Lightly spray the grounds with water, then check back at night. Odds are there will be earthworms everywhere in your coffee grounds and the ground below them. Carefully pull them out of the ground or scoop the dirt up and place them in a bucket for storage.
Make It Rain
When rain or thunderstorms fail you, you can always trick earthworms by watering down the ground on your own. Spray a concentrated spot--generally about 1 square meter--of the ground for 10 minutes. Come back in half an hour and pick up the earthworms. Another alternative to spraying down the ground is waiting for lawn sprinklers to go off, which will lure the earthworms out into the open.
Apply Some Shock Therapy
Stick a thin metal rod into the ground. Run a wire from the outputs of a 6-volt battery and touch them to the rod. This will run into the ground and send electric impulses to the worms, which will force them up above ground. However, the electric shocks can also damage the worms' nervous systems, which usually results in death, according to the Arizona Lake Fishing website.
Hunt at Night
Earthworms don't like the light and they tend to come out when it's dark. If you try to lure them out during the middle of a sunny day, your odds of catching them aren't good. Wait for dusk or darkness and use a red light if you have to shine light on anything--worms can't see the red light, so you won't be detected.