Set clears goals on every page - each page should have a specific purpose that works toward the overall goal of selling your product.
Creates easy points of contact - make it easy for your customers to contact you and build both trust and brand loyalty.
Simplify the checkout - create a checkout process that's simple to use and effortless for your customers to get your product.
Get users to come back - look for ways to get customers to come back regularly. The more they come back the more likely they are to make additional purchases.
Clearly display contact information - this will build trust and prevent your customers from becoming frustrated.
Security is important - shopping online requires customer trust, make sure you're doing everything you can to ensure your customers security.