In my field, the only way is to get the credentials, the higher you study, the more folks listen to you. It's rather difficult being an expert witness in court with a GCSE or 2. You can also command big amounts of money (relatively speaking) if you've got the pieces of paper.
However, having said that, I've met many highly qualified, published Psychiatrists/Psychologists/Psychotherapists who were as dumb as dirt and shouldn't have been allowed anywhere near other people.