There are many benefits to blogging for business. First, it can be a big
SEO boost for your site as you're adding fresh content and writing posts that most likely contain many of your keywords. Second, it can give potential clients a way to get to know you and see how knowledgeable you are, it's a great way to become an expert in their eyes. And third, it gives you an opportunity to build a community (network).
As for what to write about, your best bet is to provide answers to the questions that your target market is asking. Are you a transcriptionist, then your target market may have questions about digital recording and secure transmission of files. Answer client calls? They might like to know about virtual pbx systems and how their calls can be routed to a VA. Think about the questions that are asked of you most often and answer them with a blog post.
If you have lots of questions about blogging for business, those of us involved with Start Blogging Today conduct a Twitter chat every Tuesday night at 9pm Eastern time, just follow the hashtag #sbt10. You can ask questions and get answers from Grant Griffiths, Danny Brown, John Haydon and lots of other blog experts.