Most publishers don't want to see a biography, often called a "bio", with your manuscript submission. After all, they have plenty to read as it is. However, this isn't always the case, so don't take this as a hard and fast rule.
First off, some publishers do ask for a bio to be included as part of their submission guidelines. However, there are definitely times when including a biography with a manuscript submitted to a publisher for consideration is a wise move on your part even though the guidelines might not ask for one. In either case, you'll have to either trust the guidelines or use some common sense as to when it's most advantageous to you to include a bio.
When is it a wise move to include a bio that wasn't asked for? Fortunately, this is easy for most writers to answer. It's when you possess a special background or knowledge that makes you eminently qualified as the writer of the submitted manuscript.
What is a bio? For many writers, this usually consists of background qualifications such as college degrees and work experience. It also includes any publishing credits you might have already.
For example, if you write a non-fiction manuscript on security and have a job in the security industry, then you'd want to list that. As well, if you write a fictional crime drama and have the same background in security, then listing your background qualifications will show the publisher that he should expect your manuscript to contain realistic security procedures.
Provided you have a degree that applies to what you've written, such as in criminology, then you'd want to list it as well since it gives added credence to what you've written.
Continuing with our example, if you have already had some short stories or articles published in the security field, then you'd certainly want to list those (or a select few if you have many of them published already).
What shouldn't be in a bio? Believe it or not, many people think that a bio should list everything you've accomplished since birth. However, the bio you're submitting with your manuscript is mostly intended to first sell the publisher that you're qualified to write about your subject, be it fiction or non-fiction. Secondly, your bio will later be used to help sell your book to readers should you succeed in selling yourself and your manuscript to the publisher. So, keeping this point in mind, stick to the main points within your past accomplishments that actually have something to do with your qualifications to write about your subject matter.
So, what should a bio look like? Assuming that we're submitting All Fall Down, our fictitional manuscript used in the sample novel query letter, our author's bio might look like the following (yes, we recommend you write your bio in the third person point of view):
Ima Author holds advanced degrees in both criminology and computer security. Having worked in the security industry for the last ten years, Ima Author has provided consulting services to large corporations and the Federal Government, in particular the White House.
Ima Author has written several dozen articles on security that were published in trade journals and several widely read publications outside the security industry. As well, Ima Author has written a number of short fiction pieces that were published in several of the more popular crime fiction magazines available in the United States.
So, that's it? Though a bio can be longer, you really want to sell yourself and your manuscript in as few words as possible without leaving out anything important. So, yes, that's it.