Immediate Feedback

Theory:

We are actively engaged when our actions result in direct feedback from the system.

Application:

Can you provide a environment that responds to the visitor? Can you change the content of your webshop to the specific needs of the client? Magento for instance has the 'layered navigation' capability which allows customers to dynamically filter the content of your shop to fit their needs instead of restricting them to predefined categories to choose from. Or you could allow customers to add content to your website through (for example) reviews or ratings and showing immediate changes.