Well, if you see dirt tubes on your walls, or hear a dull munching sound, you might have termites. ...unless there is someone eating breakfast in the next room.
Termites need to maintain a high level of moisture in their atmosphere in order to survive, and so they build mud-wall tunnels which keep the moisture in, even when they are eating very dry wall studs and floor joists. They are blind and somewhat erratic, so it is usual for them to accidently tunnel out into dry air, retreat, and patch the hole with mud. So mud spots are also an indicator of termites.
It usually pays to have a professional inspect the home to see if termites are evident. After a while, professionals will notice minor indications of termites which amateurs tend to miss.
We found these by opening the wall around one small mud spot on the outside wall of an office.
Here are a few more good things to look for. Mud tubes and moisture.