There isn't one ultimate way to get traffic. Most people use a combination of some or all of the following strategies to get more people to their site:
1. Submit your product listings to Google product search (fast and free way to get more traffic) Link hidden: Login to view
Optimize your site for the search engines. Traffic Travis a good free tool to help you do this Link hidden: Login to view
2. Set up a blog on your site and create some unique and interesting content. This is also an important part of search engine optimization.
3. Use Google Adwords - although this can end up being expensive if you don't do it properly. We recommend the free training site Link hidden: Login to view to learn more.
Hope that helps! Sing out if you need help with anything else. I am happy to help :)