Using this same analogy, building a website and a shopping cart will not bring you sales in the same way that building a store will not guarantee customers. There are a number of other factors that greatly affect your success and ignoring any of these other factors will absolutely influence the outcome. Granted, you must start off by building your e-commerce infrastructure properly from the beginning otherwise you will run into problems down the line.
Lets outline the basics:
Choosing your infrastructure for your cart depends on whether you sell goods or services. The difference in infrastructure is that the buying and paying procedure is slightly different (i.e. there is no shipping step in the procedure) and typically services are a lot more complex (i.e. many configuration possibilities, multiple criteria etc..). However, this is not to say some goods are not complex in their ordering steps.
The next thing to consider is the amount of items in your store. Only several bigger-ticket items in your inventory may not need much backend, but if you over roughly 20 items then storing sessions, saving shopping carts and personalized profiles is somewhat of a must. Recent studies show that ease of shopping influences the success of a store. If you spend 20 minutes browsing a shop and highlighting several items of interest, when it comes time to checkout and you must start all over again will frustrate most casual shoppers.
Employing the most current security procedures and technologies is paramount for garnering a large userbase of shoppers. Most savvy shoppers these days will refuse to use a site that lacks in basic security features.
SSL. Secure Socket Layer is the most common technology for encrypting a users session. This ensures when a shopper is using a public internet connection such as a Wi-Fi hotspot, the other users on the same line cannot "sniff" out passwords, credit card numbers or other personal details such as shipping addresses. Enabling and configuring SSL on your web shopping cart is an absolute MUST.
Multiple Payment Options. Many customers have only 1 or 2 methods of payment (i.e Credit Cards, Paypal, Google Checkout, Money Bookers, Direct transfer etc..). If you limit yourself to only 1 or 2 of these options you will run into the problem of high dropouts at the checkout phase. Many merchants and payment processors require your site to be secure and up to industry standard before authorizing your account so bare this in mind when designing your webshops infrastructure.
Credibility. Making your shop visitors feel as comfortable as possible lends an incredible amount of weight to your success. This includes enforcing password lengths, live online help where possible, thouroughly documented FAQs and site policies and even in some cases multiple checks on payments from certain regions of the world (if you allow payments from everywhere and anywhere with no form of control you run the risk of being wrongfully flagged as a "phishing" website).
Last but not least and definitely one of the most important aspects is letting your shoppers know where you are and what you have available for them to buy. Being part of a group of shops with similar products or services where you swap links and traffic is a good start. If your website infrastructure is built properly from the beginning, the spiders from the popular search engines will eventually come and index your site and its contents.
Employing a good strategy towards SEO is imperative and in most cases is not free. Don't be fooled by companies claiming instant success for high prices. For SEO to work properly and last into the future, you must invest patience and vigilance as the game changes often and so do the rules.
A few years ago, only a fraction of Web sites had even a rudimentary bit of optimization done to them. This made it easy for anyone with the smallest of SEO knowledge to obtain some decent search results. Now with more and more companies turning to professional optimizers, the playing field is beginning to get very even and getting "ahead" is much harder than ever. Some experts even predict in a few years SEO will become too expensive for smaller companies as the fees will skyrocket. This makes it imperative to grab your marketplace slice NOW and hold onto it.