Ask HN: How do you choose a professional service provider?

If you don’t have a personal recommendation, what criteria do you use to choose a professional service provider when you need one? By “professional service provider,” I mean a physician, dentist, psychotherapist, lawyer, accountant, etc. Basically any service provider that can’t really show you a portfolio and who handles specialized or sensitive matters. Review sites by and large are not great for this, because nobody reviews their doctor or their lawyer.

I’m at a loss. Any thoughts, HN?