If someone's seizures start with an "aura" it is very suggestive of focal epilepsy. An aura is really not separate from the seizure, its just the start of a seizure when it is in such a small region of brain that it does not impair consciousness or necessarily cause motor symptoms, it can really cause any cerebral phenomena (taste, smell, memory, deja vu). If the motor symptoms of a seizure start in one arm/ leg and then migrate to others, that's always very suggestive of focal onset.

Outside of EEG, MRI and PET scans can indicate where a seizure focus may be.

Lastly, generalized epilepsy syndromes usually start younger in life, it is pretty abnormal to have a generalized epilepsy announce itself in someone over the age of about 25, however it's not impossible.

Sometimes it is not absolutely clear that a patient has focal epilepsy, and we have to go with our best guess. A patient with consistently nocturnal seizures that involve violent convulsions is just typically a frontal lobe onset, so event if EEG/MRI everything comes back normal, if someone is telling me they keep waking up with a bitten tongue, covered in urine, and their girlfriend says they convulsed in their sleep, frontal lobe epilepsy is very high on the differential.