Decide which visual details should stay
Select an adult age and a visual style, then settle on the hair, eyes and other defining traits. Review them together so the written description and the portrait refer to the same character.
Give the character a way to react
An interest, a habit and an unresolved problem help establish a personality. Think about what changes when this person is put under pressure, asked for help or faced with an unexpected visitor.
Leave the first decision open
Begin in a specific place and stop before deciding what the other speaker does. A useful greeting invites a response; it does not write both sides of the exchange.