The other comments have excellent advice, I can't add much, although I believe that good content and maintaining a presence outside of your site (getting links on blogs, other webpages, etc) is key. One thing that comes to mind is how individuals tend to search for a "background investigations" company (not quite sure what that entails). It doesn't sound like this industry would encompass very many obvious keywords, but perhaps I'm wrong. I would definitely take a look at what your competitors have over you. What makes their sites so much better (if they are)? Finally, the better you are at your business and the more people that are talking about you, the more traffic you'll get organically...it's a backwards way of thinking about it perhaps but the more of an "industry leader" you are, the better your online presence. Good luck.