Here I try to help you do legal writing. One of the best pre-law preparations I had for legal writing was to work as a journalist and an advertising copywriter. An article in Lawyers USA Online helps you apply advertising copywriting principles to your brief writing.
David Ogilvy, one of the founders of the advertising firm Ogilvy and Mather, was a master of long-form magazine copywriting. Now forms are shorter, and magazines are dying. The main long-form written persuasion that is left is: legal briefs.
Can't pass up a entry on Ogilvy in the Mad Men blog.