A good dog trainer / dog behaviorist is a professional with whom you should feel comfortable and safe. A trainer's refusal to provide a dog owner with references is one cautionary sign. Here are several others:
1. The trainer claims to be "number one", "best of" or the "only one" able to help your dog.
2. The trainer blames you 100% for your dog's behavior. Owners do influence their dog's behavior, however, there are other factors to consider in understanding your pet (i.e. breed, age, medical condition, early experiences, etc)
3. The trainer guarantees results. The APDT code of ethics clearly states:
"Members refrain from giving guarantees regarding the outcome of training, because there is no sure way to guarantee the cooperation and performance of all parties involved and because the knowledge of animal behavior is incomplete."
4. The trainer spends more time promoting books, products, TV/ Radio shows or seminars than training dogs.
5. The trainer tries to separate you from your dog claiming that she/he can get results faster without you being around.
6. The trainer offers phone or email consultations. These trainers a more concern about getting your money than solving the problem.