Before you can create credibility as an expert, you have to understand what it is. You also have to know that the definition changes according to the field you are operating within. If you are in any academic or scientific area, for example, University degrees don’t even begin to count until you achieve your masters. All work has to be completely original. You cannot “re-purpose” any practice unless you cite all your previous uses.
When you get right down to it, credibility means that you are believable. You deliver the goods that prove this. It’s about knowing how to communicate, so that your ideal clients or customers unhesitatingly realize you are the best person to help them in your niche.