1. Ensure your personality is strong enough. Don't be a doormat. Doormats not only get trodden on but, far worse, they're forgotten. That must not happen to you.
2. You must have good turns of phrase so your conversation is unforgettable too. If you can be witty and come out with appropriate one-liners, so much the better. Readers remember those. Your writer should remember that.
3. Are you prepared for adventure? Are you happy for your writer to drop you right in it, several times if need be and usually from a great height? Yes? Good! They can do what they like with you then and they will like that.
Good luck! (And tell your writer to get a move on and get you in the story).