A good wedding photographer should be a member of professional organization, such as Professional Photographers of America, Texas Professional Photographers Association, Brazos Valley Professional Photographers Association, etc. If you have someone tell you they already know everyhting they need to know, just walk away slowly. I have been photographing weddings for almost 30 years, and i am continuously learning something that helps me be a better photographer. They have monthly meetings that cover portraiture, lighting, current trends, etc.
Basic knowledge of how cameras and light work is a must. About 95% of the photographers do not know how to properly expose an image. I have had students in my class, who run studios, break down into tears because they dont know how to use their camera and cannot understand basic principles.
the 21st century has made it very easy for people to pick up a camera and start charging money for their services. Its when a person can CONSISTANTLY give good results do they show that they are learning their craft. And continuing their education is about the only way to do that, and that is accomplished by being members of professional organizations.