Finding a good vet for your pet should be approached the same way you'd look for a good family doctor.
"How long has the vet been in practice?"
A vet who's been in practice for 50 years may be more experienced, but not necessarily better informed of the latest treatments and procedures."
"Does the office have an on-site Ultrasound machine?"
This can be crucial in case of emergency.
"Does the vet do home-visits?"
If you have an easily frightened or elderly pet, this can be a great convenience.
"Does the vet have a policy of excluding the owner from euthanasia procedures?"
"Is the vet on-call for emergencies."
It may not be something you want to think about, but if your vet becomes terminally ill, you may want the option of being present for the procedure.
Is the vet gentle with your pet?
Does he or she communicate clearly and seem to care about your pet?
Ask the vet if he has pets at home him or herself.
Do you find the vet informative?
While the vet is examining your pet, casually ask him or her to explain what they're doing. This can be a good gauge of their professionalism and openness.
Ask the vet if he has pets at home him or herself.
Follow up with more specific questions and note whether the vet seems to love his or her pets as much as you do.
Is the vet's office clean?
Are the receptionists and vet techs polite to you and gentle with your pet?
Some things like that may help you choose a good one. I would say communication with both of you (dog and owner), the way he/she examines the puppy and how accessible he/she is, are important.
Although you cannot know what is the knowledge of the vet you can do a research online to see what you can find.