The golden rule of SEO is that "Content is King."  If your site doesn't provide good content, no one will want to visit it, and you won't get any free inbound links.  People don't care about your website and as such won't visit it out of the goodness of their hearts.  You have to provide something free or interesting to entice people to visit.

If your selling products, write good content about what your selling.  Product reviews, FAQs, and help files can all generate additional traffic.  Think about writing articles about your industry and submitting them to "Article Submission" sites to generate inbound links.

One of the largest factors in how you rank in the search engines is the amount of quality inbound links that your site has.  If you can get links from sites related to your industry, they will be worth more than some random link that you picked up somewhere.

The backbone of every SEO campaign should include directory submissions.  There are thousands if not millions of web directories out there, and many are niche directories that cater to your target audience / industry.  Most of these sites will allow you to submit your link for free, and many don't require a reciprocal link back.