Finding A Good SEO Company

I have a number of websites that are only getting a small amount of traffic.  I don’t have the experience or the money to spend on pay per click advertising to drive traffic to them.  I have purchased several guides in order to learn about search engine optimization and have tried my best to build the sites with this in mind.  Since I am not an expert I have likely made some mistakes and would like to consult an seo company in order to find out where I can make improvements.  I want my sites to show up in the organic listings when people search for what I am selling.