Test the earth with your own hands to see if a print will show up when pressure is applied. Then smooth down the surface again gently. If some more loose soil needs to be added to make the area impressionable, do so.

Place some sardines or cat food (the stinkier the better) in the center of the dirt circle. Leave the area alone overnight, then come back to see what animals checked out the food. Use a field guide such as Peterson Field Guide to Animal Tracks or Stokes Nature Guides: A Guide To Nature in Winter, to identify the paw prints of the critters who walked about. Looking at the track, try to determine how that animal walks. Are there visible "toenails" or claws? Some animals, like raccoons and bears walk on their hands while others walk or run on their toes, like cats and coyotes. Also look for tracks near the edge of a pond where mud often makes excellent casts of prints.