Ecommerce site does not need any specialized methods, do follow normal methods but focus on ecommerce niche.
the same as any other website would follow - keep content updated and keep adding products for fresh content.
Presuming you've got the URL structures down pat (product categories with meaningful terms in the URLs/ditto for products) there's nothing particularly different to do with referencing an e-commerce site and it's product pages compared to a regular site.
The two biggest things I'd work on (aside from specific content) is to make sure the Page Name and Page Title are rich in keywords and the actual search terms that you want to be found by. For instance, most ecommerce platforms default to the actual product name for the page name, and you can usually improve on that. One other thing is to make sure your image ALT tags are keyword rich, and that the image Filename includes the search term - you'd be surprised at the visits you'll get from Google Images.
You really need a clear plan before you start your ecommerce website. It is easy to start a website, it can be quite simple to get soem sales based on PPC but actually marketing it effectively is not simple. Get a good plan that does not rely too much on any one element of SEO.
For my ecommerce site I am using oscmax a loaded version of oscommerce and the default SEO is OK, not great. My products have basically only ONE word for the product name which is a SEO short coming so I after some tweaks I am able to compensate; here is how my SEO is implemented. Each product page TITLE has a unique title I set when creating a unique product. Instead of the default "Butterfly : $64.99 - Website Name" the new title shows "Butterfly Illuminated Wall Decor and Glowing Home Art" Then the product name is wrapped as a H1. I also have an H2 with a few keywords that says something like "Illuminated Wall Decor" The product description is keyword rich without being awkardly worded or spam like. Also the product name is listed other places on the page to increase the product keyword %. The product images I changed from "butterfly.jpg" to "butterfly_illuminated_home_decor.jpg" As Jen990 stated, having a plan really helps.