Credibility depends on competence and sincerity. It is the ability of a message to be believed, this quality is closely related to authenticity, honesty and trust. But it also depends on the competence of their knowledge, the ability to provide adequate information. Likewise, education, occupation, place within the hierarchy of the organization, experience and ability to communicate have a great influence. It implies being recognized for possessing solid knowledge and experience and becoming a role model and who to consult. It is a skill that is gradually gained.
For example, in one of my jobs, as head of production in a media company, I had a team consisting of 7 people. Almost all of them were in the position more than 5 years ago and had a way of working. When I arrived, with a new methodology, innovative, at first I gave them space. I began to observe his actions and gradually go sliding some of my proposals. They tested them and when they saw that they worked, they incorporated them into their work routine. That way, I gained their trust without imposing my ideas and they had me as a reference. We achieved a very enriching teamwork.