What are the necessities?

Just as in traditional commerce, especially that done by mail order, there are certain elements required to perform online business. You must :
Promote your Web site presence
Have an online catalogue or store
Have the capability to receive payments
Be able to deliver the item
Provide after-the-sale support

— Website promotion —

You need to advertise and promote your business, so that the customers will either come to your store, read your catalogue or view your Web site.

— Online catalogue or store —

You need to have a store or catalogue where customers can view and select goods or services. Customers need to be able to easily get around your catalogue to find things. The customer should be able to easily browse the selection and mark products for later purchase. They also need to be able to information or see pictures of the items.

Finding items

The Web site should be easy for customers to find what they want. The customer must know what is in the store, and the products must be organized in a logical manner.
The customer must be able to easily search for what he or she wants without the help of a sales clerk.

Selecting what to buy

Once the customer finds what he is looking for, he can put the selection in a "shopping cart" and search for other items. This make it easier for the customer to purchase multiple items, as well as to buy things he may not have been looking for.
Just as in a physical store, people often buy things they just happen to see. For example, stores place some "impulse items" at the checkout stand.

— Purchase —

It should be easy for customers to purchase the items they want. You must have a way to receive online payments, either using credit cards or other means of payment. For example, business-to-business sales may simply involve a purchase order.
The purchase of the item can be complex, but it should be made as simple as possible for the customer. The customer must give certain information about himself. Usually this is name, address and e-mail. A mutually acceptable payment method must be chosen. Credit card or billing information must be gathered. The merchant must process the customer's payment information. Finally, the customer must receive confirmation of the sale. Security is a concern in credit card purchases and the ability to encrypt transfer of data.

— Delivery —

You must have a good means of fulfilling the order and delivering the material to customers. Different means of delivery depends on the type of item purchased.
The product may be access to special information on the Web site, it may be downloadable software, or it may be items that must be physically delivered to the customer.

— Support —

The customer needs a way to voice problems. You also need a customer service system, consisting of support to handle complaints or returns in the event of problems.