They have to know how to "peel the onion" layer by layer of your body's health problems. The first naturopath I went to gave me all very good supplements, things my body needed (as determined by blood, saliva, stool tests), yet I didn't get any better. I was taking 20+ supplements every day. I now know my body didn't know how to handle that much "good" stuff at the same time. I had been trying to "take chunks out of the onion". For example, my body may have wanted to focus on healing any issues with my gut, yet giving it tons of supplements for my liver function, kidneys, and anemia weren't following what my body needed at that time.
Then you have to go down the path of asking yourself whether you believe in musle testing/your body knows what it needs. It's contoversial, and even I have my doubts sometimes. The above naturopath mentioned did not muscle test.
The new naturopath I see (I'm on the west coast) believes in muscle testing regarding foods/food allergies and supplements. He tests the individual supplements on my body before prescribing them. My naturopath is also a chiropractor and knows in depth knowlege of neuropathy, among other tidbits like iridology. I have seen some improvement recently involving my neurological function.
Hope you have success, and sorry I don't have any better advice.