There are many good articles for you to look at; simply search for eCommerce site design or similar keywords.
Keep people, your buying customers, in mind because everything you do is to fulfill their desire:
- Don't get hung up too much on the platform. I've settled on Magento, and there are many others. A WordPress plugin may be enough for a few specialized products. You can find a hosted solution if you don't want to deal with the store technology.
- Traffic matters. People must find your product!
- Presentation matters, so use eye-catching graphics and be concise with descriptions.
- Include related products but don't overwhelm.
- Make it easy for people to link, like, email, and add your product to their wish-list because people don't often buy on their first sighting.
Take some time to learn about:
- analytics tools
- keywords and search engines
- product categories and descriptions
- page layout and hot spots
Here is a great place to start:
