The foremost thing is that the chiropractor must be certified from a recognized body operating in your country so that to ensure his authenticity. For example in one of the body is American Chiropractic Association.
You can go for the word of mouth if any of your friends or family already visiting a chiropractor. If the chiropractor has already built the reputation possibility is that they would be advertising no more. So suggestion from a known can be good.If you are living in Canada, you can look for chiropractors in bowmanville online.
Also have a detailed information about the techniques being used by the chiropractor for treatment. You can know about the specialty of the chiropractor.
Your chiropractor must be honest to you while the treatment. If he is not able to find the best solution to your treatment he must be honest enough to refer you to some other chiropractor.