basically, search engines base a lot of their rankings on how many good, quality links you have coming in to your site.
really, the biggest thing is content. For example, if your page has the header "Bob Ross" it is more likely to come up in a search for Bob Ross than if the name is mentioned in a larger block of text. Also, the more words on your page, the more possible keywords. The problem with this forum is that it is not static; the content is changing very very quickly. Also, the forum, isn't very spider-friendly. While the "open thread" links are convenient for us, my guess would be that they might be giving those spiders a little trouble.
I won't pretend to be a complete expert, but I have deffinately done a lot of work in this area.
Also, this might help:
http://en.wikipedia.org/wiki/PageRank
)
Supply Centers Ignored in Autumn
)
)
)
)
)