We're many months away from even starting to look for someone, but I'm curious and like to plan ahead

If you're looking to hire someone (a stranger, not a friend or family member who you already know and trust) for full-time long-term child care for your newborn, how do you do it? Where do you look? What qualifications would be required? What do you ask to ensure applicants are qualified? What are your absolute deal breakers?

Thanks