Free 1 month paid account as a teaser
Short, concise description of the idea
Basically, when you order cable TV, there's always a time when the cable company is giving away a free weekend of one of the premium channels, hoping you'll like it and order it. Livejournal should have something similar to entice more paid account purchases.
Full description of the idea
A similar scenario was this BBS in town more than a few years ago. When you signed up, you got a free week of full functionality. It showed you why it was worth paying. I have a feeling most users have no idea the coolness level the benefits of a paid account bring.
An ordered list of benefits
An ordered list of problems/issues involved
An organized list, or a few short paragraphs detailing suggestions for implementation