Also ask around at your local herp clubs. They can give you names of good vets that people there have found as well. the ARAV list is decent as well but since you don't actually have to pass any kind of tests and just need to pay yearly dues to get the membership, I can see it becoming a selling point more than an actual "meaning". I know as an automotive mechanic, the ASE tests didn't necessarily mean you knew more than a guy who didn't have the ASE certification, it just meant you were good at taking tests. But also those certifications required tests to be passed, not just a monetary amount be paid. Of course I could be way off on the ARAV but I would still say check with your local herp club as they would know from first hand experience.
Vets can be needed for anything from an RI to surgery. Luckily I've only had to see my vet for RI in my bearded dragon(knock on wood). Generally most vets who see mammals like dogs and cats don't see reptiles or amphibians as they need a whole different set/size of tools and equipment to deal with that, or so I've been told.