1. Imagine Your Audience
Would you use the same approach to ask for a date that you would use to ask for a job (assuming that asking for dates isn't your job, obviously)? Business owners or representatives need to introduce themselves, not just to the public, but to their public -- the specific target audience that they aim to cultivate. Think hard about exactly who constitutes the ideal reader of this bio. What do you want that person to do -- offer you a job? Check out your products and services? Recommend you to an associate? Focus on telling that person exactly what they'll want to hear as a means of triggering that response.
2. Match the Surrounding Tone
I've been called in to rewrite employee bios that stuck out like broken teeth on the client's website. in many cases, they simply didn't match the style and tone of other previous bios, or of the site in general. There's always one guy who insists on providing 500 words when everyone else has made do with 100 (or vice versa), or a first-person address in a sea of third-person entries. Some bios may seem overly friendly or even childish within the larger context of the page, while others may seem dry and stiff. If your bio will be added to a general bio page, read the existing entries carefully and try to match their tone and length.
(The exception to this rule comes when you've been asked to provide a bio that will sit next to your competitors' bios on a directory page. On those occasions, by all means stand out, as long as you can do it in a way that scores points over neighboring entries instead of making you look silly.)
3. Keep It Clear and Readable
A bio is not a resume. Your goal is not to include every single detail of your professional, academic and personal life; it's to get the reader interested in who you are and what you offer. Ever looked at the author bio on a book jacket? In most cases, you get the least you need to know, just enough to make you think, "Wow, this author has some impressive credentials. I think I'll give this book a shot." Feel free to write a long draft, but be willing to go back and cut (and cut, and cut). As for word choices, go for clarity above all. Impress the reader, not with your vocabulary, but with the high points of your professional history, skills and experience.
Good luck with telling your story -- and if you need help, just let me know!