The bio should simply reflect who you are. Most of your clients will never read it. And if they do, you want them to see that it's the real you.
Some agents are successful with very homey and personal bios... talking about their pets and their kids. Others prefer to use an almost resume-like list of dates and accomplishments.
Just be you. Are you the friendly neighbor agent who will bake chocolate cookies to serve at open houses? Or are you the accountant type with years in the mortgage industry who will assist with all the financial details?
The big thing I'd recommend for ANY agent is to have someone PROOF-READ their bio, their web site, and any materials they prepare such as flyers, marketing brochures, etc. There's nothing that turns me off more quickly to ANY business than typos, spelling errors, and poor grammar.