On-Site SEO
1. Home Title (title of your website) should reflect your main keywords
2. Use SEO-friendly URL
[ie - http://www.example.com/white-denim-jeans instead of http://www.example.com/productid_9399]
3. Repeat your Product Title's keyword in the description
[keyword density of 6~8% is good]
4. Integrate a Blog so you have fresh content
5. Internal Linking: in your product page, recommend another product that is perhaps similar or if you have a review on your "blog", link it there.
[when you link it, don't say "go to http://www.example.com/xxx" - instead use keyword rich title that links to your review page: "White denim jeans review"
Off-Site SEO
1. Integrate account with Google Webmasters (also Bing)
2. Submit url to multiple search engines
[just type submit url and u'll find useful services for free]
3. Submit ur shopping site to DMOZ
http://www.dmoz.org/Shopping/
4. Quick Index your website so sites know about ur site:
http://www.affmastermind.com/toolbox/quickindex/
5. Use Social Media (twitter, facebook pages, etc) and post your url with relevant keywords
[ie: you can buy white denim jeans here: http://www.example.com]
I hope some of these tips were useful

Any more Basic SEO tips??