An author biography is a brief credibility building statement that can be used to introduce you to your target fiction market. There are two levels of detail in your author biography: the tag line and an extensive biography containing relevant information concerning you as an authority in the type of book you have written.
Depending on what type of book you have written, you want to blend that into your bio. If you write a book about a typical family, you may want to say that you are a happily married person with children. Or if you wrote a book about suicide and you established a Suicide Awareness group in your community, you may want to include that in your brief author history.
Your tag line on your bio is like a headline of a newspaper article. This is your initial introduction to the world using your author biography. This should be in the form of one powerful sentence including your name, your related or relevant position or occupation, and where you are from in the world.
Once you have a tag line, you want to jump right into your extensive fiction biography. This goes more into detail about who you are, what you do for an occupation, and what your primary interest is in (if the biography is for a specific book, you should be primarily interested in the subject of your book).
Write some publishing bullets that relate to you book such as if you have written articles on suicide or articles on family life. If you are a member or leader of a local group that deals with suicide or family advocacy, you should definitely include that.
Conclude your author biography by ending on a note of where you live and have lived, with whom you live (husband, 2 children, a cat) and if this is your first or fifth fiction novel.
As a fiction writer, it is easy to understand if you can't find too many things that make you a credible authority in a particular subject. However, if you researched your topic thoroughly, you can elaborate on that fact. If you've participated in a fiction writer workshop or helped out at your local schools with creative writing, that establishes you as a credible authority as an author.
If you don't have many (if any) credibility bullets for your author biography, you may consider joining groups in your community that center around the primary subject of your novel.
For more help with creating an author biography, below is an example of an author biography that will show you the proper structure of an effective bio.
The following example came from Lulu.com and will show you the general breakdown of how your professional biography should be written. There's not much to a simple bio and it can be used with your query letters, brochures, articles, and press releases.
A biography is basically synopsis or summary of you, your life, and what makes you an expert in what you are writing about, generalized to the point of one or two sentences. Short and sweet is what you are looking for here.
Some of the highly recommended elements of your bio should be to include your full name (as you want people to recognize you as a writer which may be a pseudonym), what you do for an occupation or a living, and some supporting data that portrays you as an expert in the subject you write about. This is a little trickier for fiction writers, but if something about you relates to your story's topic, then use it in your fiction biography.
Always write your biography in third person voice so it sounds as though someone else wrote it for you. If this is difficult for you, you can ask someone else to write it for you, preferably someone who knows you quite well like a relative, spouse, or very good friend.
Here's the example of a fiction author bio from Lulu.com:
The Tag Line: Jane Smith is a Practicing Physician in Rumford, Maine.
A Tag Line is much like a headline but introduces you, what you do, and where you live all in one sentence.
The Extensive Bio: Jane Smith, a practicing physician, has been a Civil War buff for decades. She has published articles in Civil War Journal, Civil War News, and Civil War Weekly and is a member of the Civil War Society. She lives in Rumford, Maine, with her husband, three kids and two dogs. This is her first novel.
An extensive bio expands on all of the information in a tag line, going more into detail about you and your life and how it affects your writing. It also shows whoever is reading your biography how you are an expert in your field of writing.
As you can see in the biography example above, it was kept short and sweet and established her credibility in the field of the Civil War, the center topic of her novel. It shows how she is a professional as well, portraying her as an educated woman with a family.
It may take some time to write your biography, but the time you spend on it will be well worth it in the long run when it comes to boosting your marketing efforts.
Some of the common uses for a biography would be to add it to your blog posts, your publisher applications, press releases, author website, or articles about your book's subject. This is a great way for people to get a quick picture or who you are and what you do.
Once you have written your biography by using the author biography example above, add it into your book press release to help beef it up as well.
Here's a great source of actual author biography writeups that you can check out to help you write your own.