How do you refer to an author again in a paper? I first said her full name but what do you do on the second reference?

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.