Blogs are online journals - dated entries discussing anything from the state of the economy to new product launches.
Blogs can be used to communicate your expertise to potential clients, provide a resource for existing clients (for example Richard Murphy's blog about tax research) and even to gather information about your readers to proactively target certain markets (of which more here if you're interested - a good PDF guide to competitive intelligence gathering via social media).
If your blog is well-written, original and not overtly self-serving, it can be a valuable marketing tool and boost your online profile, both in Google's and your clients' eyes.
For those just starting out, we recommend The Blog Coach as your first port of call for how-to guides.
If you're worried your client-base won't be keen on the 'blogosphere', you can provide tools on the blogsite allowing your posts to be synced (send updates direct to inbox); posts can also be sychronised to appear on other web pages.
This can be an excellent way of translating traditional forms of reciprocal business recommendations to the web; for example, an estate agent might wish to sync blog posts from a recommended conveyancing solicitor, and vice versa.
Blogging is also a great way of creating content linking to your site - which Google loves.
Most of all, blogging can be a great way of interacting with your community.
Your original and interesting post is just the beginning of a larger conversation.
As your readership expands, their comments on what you have to say can extend and develop the topic, providing you with feedback and further ideas for new posts.
Post-script, 14th August 2019: the website 'The Blog Coach' appears to have shut down. We have retained the reference for historical interest, but would advise looking around for other, similar guides to blogging today.
Continue to Guide to Business Uses for Social Media Part 6: Twitter