There can be a number of causes of headache and they constitute a lot of time in neurology and neurosurgery clinics. The commonest headaches are tension-type headaches, then migraines. There can be headaches that have "red flags" including changing in position, worse at various times of day, altered neurology or evidence of meningitis.
Time: are they acute, how long have the headaches been there, how long do they last?
Location: uni/bilateral, frontal, occipital?
Position: worse or better when standing/lying/moving?
Associated: nausea, neck stiffness, photo/phonophobia?
Recently post-partum. Had headaches as teenager. Now severe headaches.