Longtime blogger and marketing pro Jeneane Sessum wrote "To Blog or Not to Blog: Blogs Help Corporations Answer the Call to Conversation" (pdf) for businesses, but her clear, readable how-to will get anybody up to speed and keep you from falling on your face if you're considering blogging. The crux of it:

Companies don't blog; people blog.

...A sure way to drive readers away is to write a blog using a corporate voice rather than the discernible, unmistakable voice of a human being. The key to business blogging is that people -- not the business -- read, write, and respond....

One thing you can't hide
Is when you're crippled inside.
-- John Lennon