If your site has content/features that are in demand and there are no competitors that make your site obsolete in comparison, the traffic will come. If the traffic comes and they like what they find your site will market itself.
Rule 1: The most important thing is that your site is as good as it can possibly be and that people will want to use it.
Rule 2: Make sure that if you are going to try and optimise your website for search engines you don't do anything that does not comply with these basic guidelines:
http://www.google.com/webmasters/gui...s.html#quality
If you strictly keep to these two rules your site will potentially be a hit.
Some tips:
Fresh, original content - since you have a message board this should be no problem - make sure you moderate it carefully to avoid going against rule 2 and aim to achieve rule 1.
Links to your site: If you achieve rule 1 your site will naturally get loads of inbound links. These links will be ideal for
SEO: related, keyword rich, one way natural links.