Start your bio sheet by highlighting your main acting achievements. Don't list everything -- just the most recent and most impressive credits you have.
Add some background details about what got you interested in acting and how you got to where you are now. It's okay to inject a little personality here.
Review what you have written, making sure your sentences and paragraphs are short and easy to read.
Make sure the bio is written in third person throughout. Be consistent with your name -- stick with either first or last after the first full reference.
Keep the bio to a page or less. Make sure the formatting is consistent and that it has no spelling or grammar errors. You can print your finished bio and mail it, hand-deliver it or send it by email.