After making sure that your pages are optimized with proper keywords and meta tags you can contact any of the more known SEO companies. You can test drive them and see if their marketing efforts are something that bring you results. If not, look for a new one.
If you need professional help we recommend to do a Google search. There is no better proof for an SEO company, than ranking on the first page of Google for the term.
If you are a do-it-yourselfer, your best bet is to write great content and try to connect with bloggers in your market. You may also decide to promote yourself further by doing classified ads and other methods. We highly recommend the use read Google’s quality guidelines and read up on some forums, not to make mistakes that would later strike back.