What to write? Write about what frightens you.
Fear is a map. It tells us where we lack experience. It shows us where we perceive our boundaries to be.
Oedipus killed his father and slept with his mother, but he did not know this till he and his mother were told by the seer, Tiresias.
Your character’s life told in the narration halts your story’s forward motion dead in its tracks, whereas one or two well-dramatised scenes can powerfully represent that past life and at the same time keep your action moving.
It is your business to write what other people think but don't say. Go for the throat.
Start with anything that bothers you – be honest, be angry.
Remember how people react to a car accident. Highways choke up as drivers slow down to gawk. It comes as no surprise that news programmes concentrate on bad news first. That's what interests readers.