Personal recommendations from others with similar provider needs is, of course, the best way.
But failing that, this can be quite difficult, since there aren't simple, consistent markers for this kind of expertise in a provider. So far, I've found the easiest approaches are to try to screen providers by proxies for giftedness, and to interview carefully. For example, in a provider's own educational history, diverse, interesting (e.g., not just the standard biology bachelor's) fields of study prior to medical school, or an additional academic grad degree besides the MD. Or a degree from a highly-selective institution (not that the right kind of person is limited to any of these educational markers).
And on interview, I'm looking for someone with intellectual curiosity, who dips into the research and practice literature on a regular basis, to keep current, in addition to in response to specific situations, and who appears inquisitive about multiple topics. Definitely (as one would always hope) someone who is sincere and proactive about collaborative decision-making with me as the parent, listens to both my child and I without condescension, offers their thoughtful and data-supported recommendations, and then allows me to parent.
(We love our current ped, who always cites research when making recommendations, and will give us options, each with their associated risks and rewards. They know we are quants and evidence-driven, and deal with us accordingly.)
