What should one expect during the physical examination for sinusitis?

Varies. You can expect at least an inspection of the nose with a speculum, looking in through the front of the nose. The doctor may also elect to use a scope to look further into the nose.
Endoscopic exam. When an ENT surgeon examines you for a sinus infection he will do a complete head and neck exam. You may also have a nasal endoscopic exam - very easily done in the clinic. This is using a telescopic camera to look in the nose a sinus passages.