Best Practices for Legal Blogging has created a guide to Best Practices for Legal Blogging.
Why should you care? From the article:

As the use of blogs as a marketing tool proliferates among lawyers, differences in quality between blogs covering the same topic will become evident. There are only so many blogs that prospective clients can read on a daily basis, and as the number of choices grow, readers will become more and more selective. It is therefore critical for any lawyer launching a blog to consider best practices that will set his or her blog apart from the pack.

Source: Law Librarian Blog