Well, you can't control the list, but if you aren't marking a forum as read, I highly recommend doing so. Then the next time you go back in you can tell based on the font which threads on the list have new content, and if you click the blue dot/star on the left it'll jump you to the first unread post.
Even if you don't mark the whole forum as read, that's still a helpful way to view threads and keep track of where you left off.