How does a dentist diagnose a dry socket other than hearing a patient say he has pain and a foul taste?

Sight and symptoms: Dry socket is essentially the early breakdown of the blood clot in the extraction site, leaving (for lack of a better term) a big hole. Symptoms will usually start between 48 and 72 hours. So basically if everything seems to be going ok then 2-3 days later you're in severe pain with no blood clot in the extraction site...That's dry socket.

Exam of socket: The area of an extraction site is a nutrient rich area that is trying to 'fill in.' when a disruption of the healing site occurs, the clot gets 'pulled out.' post-operative instructions include leaving the socket undisturbed to promote good healing. If the wound opens up, bacteria, food or air can penetrate into the jaw bone which can be quite painful. Follow directions or see your dentist.

It's easy: Those two symptoms are usually enough to assume there is a dry socket. However, unlike a socket that is healing normally and has a blood clot filling the socket once occupied by the tooth, when we look into a typical dry socket, we see a hole and usually exposed bone instead. The different appearance between the two is pretty obvious.