You see one. (Duh!)

Your pet(s) seems to be scratching more than usual lately

Look for “flea dirt.” Flea dirt will look like tiny, dark specks. These specs are actually small bits of dried blood that have passed through the fleas’ system.

If you suffer from flea bites yourself, especially on your ankles.

Trick: Put on long white socks, turn off the lights, then walk around over likely areas. Turn back on the lights and check the socks for fleas.