There is no perfect way to find a good plastic surgeon but two main factors are the qualifications of the doctor and the doctors personality.

There is no perfect way to find a good plastic surgeon doctor and you need to take into account many factors.
The two main factors are the qualifications and the doctors personality.

There are many ways you can find out about a doctors training. 

The simplest is to ask. 
Most doctors are happy to provide you with information about their background and training. 
If they are not, then you a justified in being suspicious.

There are many professional organizations worldwide that publish lists of their members and this is often a good starting place. 

In the United States the American Society of Plastic Surgeons has a doctor finder web page which may help you. 
They also provide a toll free number 1 800 635 0635
You might also ask if the doctor is board certified in the field of plastic surgery. 
Although this does not guarantee a good result it does
tell you about their training.

You can try to talk to your family doctor and local medical association. 

They have a personal knowledge of a plastic doctors reputation. 
Nurses and people who work in hospitals also have first hand experience of a plastic surgeon.

Check in your community and talk to people who have had plastic surgery. If a plastic surgeon is getting consistent results, you may be able to discover this by word of mouth.

Local hospitals have training requirements to allow doctors to work on their staff. This is a good place to start your search.

The second factor, the doctors personality, is also important. You can look at it this way. If all goes well, which it does in most cases, you will see the doctor only a handful of times. However, if you have a problem, you and the doctor are going to have to work through some difficult times together. You need to get on well with the surgeon, and the plastic surgeon with you, under some trying conditions. Talk to several plastic surgeons and you will soon get a sense of the ones that you like and can get on with. When the doctor you like is well trained you have a good combination.