What is the best way to discover the voice of your narrator?

It seems like one of the best ways to ensure a story or novel is compelling is to have a strong narrative voice. Sometimes I can have difficulty writing in the voice of a character. There are times in which I have to rewrite sentences half a dozen times, because they still have the tone of my own voice, rather than that of my narrator. Also, sometimes I have trouble finding the voice of my narrator in the first place.<br><br>So, what are some of the best ways to develop the voice of your narrator?