Language forms, particularly oddities of pronunciation and syntax, that are peculiar to a region or a group. Avoid using dialect if it renders the speaker as ignorant or makes the person a subject of ridicule, even in quoted material. In rare stories, use of dialect may be approved as bringing a sense of atmosphere that could not otherwise be achieved. Such approval should come from the department-head level. Obviously, further exception is made when dialect itself is news, such as in a story in which it is pertinent to the identification of a crime suspect. If dialect is to be used, words are spelled phonetically and apostrophes indicate missing sounds. Be accurate and avoid exaggeration.
REFERENCE: NABJ Style Guide