If you are talking about citing an author's work during an in-text citation, first it depends on whether you are using APA or MLA style.
Under APA style, after the first full reference, you would cite the author the second time in parenthesis with last name, comma, the page number, comma, and the publishing date. IE: (Wagner, 3, 1984)
Under MLA style put the author's last name in parenthesis with the page number after it, but no commas in between. IE: (Wagner 3)
If, however, you are talking about journalistic style as referenced in the AP style book you would refer to an author or any other person by full name on the first reference, and by the last name only on the second reference.
Hope this helps.