Ethan Zuckerman put together a set of tips and reasons for live blogging at conferences: The 5-4-3 double play, or “The Art of Conference Blogging”.
The Enterprise 2.0 Conference was the first time I tried conference blogging. I found it to be a great way to keep notes. I have a stack of hand-written notes from prior conferences that end up sitting in the stack. By blogging at the conference, it combines the note-taking with putting the notes into a useful repository.
I went with Ethan's template method. I set up a draft of the blog post prior to the session. Actually, I combine setting up the draft posts with setting up my schedule. As I decide on my session options, I create the draft blog post. That way my list of draft posts is also my agenda for the conference.
I would do a little Google research into the background of the speakers and set up hyperlinks to a relevant site.