First off, content is king. Basically, your site has to look like it knows what it's talking about, well actually it has to prove that it knows what it's talking about. The more valuable content you have on your site the more valuable your site will inherently become. Google likes big sites with a lot of rich content. Content is your first step, but it should be a never ending process in maintaining your site. After your core pages, (Home – About Us – Contact Us, etc.) you should implement someway to consistently update content.