Specific strategies that a speaker can use to enhance his/her credibility

A speaker needs to be viewed as credible in order to persuade an audience. What are specific strategies that a speaker can use to enhance his/her credibility? How can those strategies be implemented before and during the speech?
In order to receive full credit, please write 1 main point in at least 150 words by Wednesday. Afterward, please post 2 replies to classmates which should be at least 100 words each by Friday of the close of this lesson.