The following was the response I sent to a reporter who asked that question for a story she was working on last June and was published in October:
This is an issue we address quite a bit with clients and for ourselves within our e-Strategy practice.
Before even crafting your bio, you should think about how you want to use Twitter. To give a few examples, we counsel clients on using Twitter as an expert positioning tool, as a media-relations tool, and as a customer service vehicle. Then think about the audience(s) you want to reach through Twitter. Who are they, why would they want to follow you, and what search terms would they use to find you if they didnâ€™t know you?
Your bio, then, should be written with those keywords in mind while also being compelling enough to create an interest in following you.
I use my account as an expert positioning and a media relations tool and as a lead generator: http://twitter.com/derickson My bio, therefore, reads:
Tunheim Internet marketing/strategic communications/PR guy, estrategy & social media fan, political junkie, football & baseball fanatic, blogger.
Iâ€™ve included keywords for the audiences I want to attract will likely be using to find someone like me. I also add some personal information to give people a way to relate to me as a person; this also serves to manage expectations so people wonâ€™t be surprised and/or annoyed when I tweet about sports.