To paraphrase James Carville from the 1992 presidential when his "it's the economy stupid" first entered the American consciousness: "it's the content stupid." There may be many ingredients in building an audience for a blog, but whatever the strategy, first and foremost you must start with the basics. Do you have something interesting to say? Lawyers write for a living and therefore this initial threshold question is not as problematic as it might be for other professionals. Clearly, not all lawyers can readily meet this requirement but a certain percentage will not find the transition to blogging all that difficult, at least not from a writing perspective.
However, a far more subtle question is whether they can get "plugged into the conversation?" The latter requires establishing relationships and commenting on what other people are writing in a manner that motivates (compels?) them to comment on your "stuff." Why is this important? Several reasons come to mind: 1) monologues are not much fun; 2) more importantly, if you are blogging from a business perspective then those inbound links are crucial to your search engine rankings. Many of the "how to blog" tips (e.g. top 10 lists) are designed for this purpose. As cheesy as these tactics are, and lets face it, cheesy is probably the most complementary thing we can say about them, many bloggers engage in this behavior. Why? Because in on-line marketing the search engine is king and we must feed the monster the inbound links that it/we eat for a living.