One of the main issues I see is that people assume that if they setup their website, then Google or some other mystical force will help them sell their product by driving customers to their site. The simple truth is that generic/organic SEO isn't a driving force for sales. That was the case 10 years ago, but it simply is not the case anymore. Google has changed the playing field to prevent SEO from working as a driving force. They saw too many SEO experts tweaking the results and they have eliminated that ability now. Google does not really use SEO when other metrics are available for ranking. SEO is now really only important to make sure your site is displayed under the correct keywords. Not how it is ranked.
Many website owners ponder that question every day. As website owners, we are bombarded by phone calls and emails that tell us that being inserted into directories will help us. For as little as $99 a month, their service will insert us into 100 different search engines.