Anyone can use the title
No license is required to train dogs for a living. Certification is voluntary, which is exactly why it is worth asking about: each one tells you something specific about what its holder has been tested on.
What the certifications require
CPDT-KA, from the Certification Council for Professional Dog Trainers, requires at least 300 hours of dog training experience in the previous three years, at least 225 of them teaching, an attestation signed by a certificant or a veterinarian, and a 200 question exam covering learning theory, instruction, canine behaviour and welfare, and professional ethics. Holders sign the council’s code of ethics and its least intrusive, minimally aversive policy, and recertify every three years through continuing education. CBCC-KA is the same council’s behaviour consultant credential.
The International Association of Animal Behavior Consultants accredits trainers with at least two years of experience, and certifies behaviour consultants with three or more years working complex behaviour cases.
Other certificates are issued by the school that taught the course. That is not a criticism, but the school set the syllabus and marked the exam, so ask what it required.
The method question
The American Veterinary Society of Animal Behavior recommends that only reward-based methods be used for all dog training, including the treatment of behaviour problems.
It names what it means by aversive: electronic and shock collars, prong collars, choke chains, leash corrections, citronella collars, physical punishment and shouting. The documented risks it attributes to them are fear, anxiety, stress, aggression, stress-related illness, pessimism, and a worse relationship between dog and owner. It also states there is no evidence that aversive methods work better.
This is the one place where a strong opinion is not ours. It is the position of the veterinary specialty that studies the subject.
Five questions before you book
What happens when my dog gets it right? What happens when my dog gets it wrong? What equipment will you put on my dog? May I watch a class before I enrol? What are you certified in, and when did you last recertify?
The second question separates trainers. A clear answer involving food, a toy, or a pause is a good sign. Vagueness about "corrections" is also an answer.
What should make you keep looking
A guarantee of results. Talk of being the alpha or of dominance, which has its own veterinary position statement saying it misreads what dogs do. Refusing to let you watch. Refusing to name the equipment. Telling you to disregard your veterinarian.
Puppies: start earlier than feels safe
The window that matters most is roughly the first three months, when a puppy is more curious than fearful. AVSAB’s position is that socialisation should begin before the vaccine series is complete, and its argument is blunt: behaviour problems, not infectious disease, are the leading cause of death in dogs under three years old.
In practice classes start around seven or eight weeks, after a first set of vaccines and a first deworming, held somewhere cleaned between groups. Ask your veterinarian what applies to your puppy, and ask the class what it requires before the first session.