I am pretty sure that my pet has a flea problem, but I can't tell for certain.  Any suggestions?

A flea is a tiny, laterally flat and wingless insect that subsists on the blood of its host. Fleas have long legs that enable them to jump tremendous distances and they can quickly crawl through your animal’s fur. Check your cat or dog frequently for fleas by brushing them over while they are standing over a white sheet or towel; flea feces—small, black flecks of digested blood—will fall off easily, indicating the presence of fleas. A flea comb with very fine teeth is helpful for removing flea debris and may remove some adult fleas if enough are present.

Most fleas congregate over the rump and tail area of the pet. If evidence of fleas is noted, the animal should also be checked for tapeworm segments, which appear as cream-colored, rice-like segments stuck in the fur around the anus or in the feces. Consult your veterinarian for recommendations concerning flea control and prevention.