Designate someone to represent your audience

Stephen King advises that you designate someone you know, you trust, and whom you think represents the audience of your work to act as “The Reader.” Then, write for that person. They don’t even have to know that you’re doing this. In his case, it’s his wife, and she eventually does read his drafts, but he always keeps her in mind when writing and directs everything he creates at her. -- Gareth Branwyn, How to Be a Better Writer