This small piece of information (160 characters on twitter) about you or your company can make a big difference to your profile and the number of your followers.
If you are looking to increase your followers they need to know who you are and what your tweets will be about. If your bio is not descriptive it will put people off following you. Focus on the key words relating to your industry and incorporate these into your bio, this will also help with the SEO angle of your profile.
Personally I want to know what you do, your area of expertise and where you are based. Make sure that you have your web address on there too, as many people using twitter are looking for a service and the more information that is available at their finger tips, the better your chances are at securing a new client.
Why not test this theory and let me know how you get on, there are many statistics out there that demonstrate that having a complete bio will help to increase your following.