I've looked into SEO for a few projects - most of the old tricks are a bit tough to get working due to well, everyone doing it.
The key is content, content and content. Start writing articles (if useful for potential buyers even better!), back linking to the site and keep it up. Try and get featured in local/national online newspapers/sites too and getting them to link to your site. The more you build your online presence the higher you get ranked. Easier said than done of course!