How do you find good instructors/mentors?

You find good mentors by moving around to be honest. How do you know the trainers aren't good, have you met or talked with all of them? I think any respectable trainer has one thing they can pass on to a person, and with each trainer you can learn something new, like a new technique. But it's still true, you can't just stay in one place and allow the trainers to come to you. I would think attending horse shows, even if you aren't riding, and talk to the trainers at the show. Attend clinics in your area and outside your area if it's possible. I learned a lot of things from attending horse shows and clinics, and met a lot of knowledgeable people in the field.