One of first things online entrepreneurs have to recognize about Internet is that it's a very impersonal medium. When you're selling something to someone in direct conversation, you have opportunity to create rapport and inspire trust in them. You can answer any questions they have, and you can guarantee their satisfaction.
However, on Internet, all customer has to go by is your image and your written word -- in other words, how professional your appearance is and how well you address their concerns. Both are equally important. You've got to provide customer with a site that looks nice and has all information that they want.
Designing a professional website is beyond scope of this article, so I won't address it here. However, let's take care of "information" part. Here's information you need to have on your site to really start generating sales:
1. Clearly stated benefits
Somewhere on site you need to tell customer why product they're going to buy is better than competition's and why they should buy it from you specifically. (In other words, with what benefits do you provide them?) This information should be given to visitor as soon as possible. (The home page is best place, if possible.)
2. Evidence of superiority
You need to *show them* (not just tell them) that your product (and your company) is superior to competition's. You can do this through a free trial of your product, a tour of product, etc. You also absolutely must use another method: testimonials.
Testimonials are one of most powerful marketing tools in existence, and by adding them to your site you can increase sales dramatically. (A note about testimonials: you should never, ever make them up, and you should always include full name of sender and their e-mail or website address when possible.)
3. Answers to their questions
Customers that are interested in your product are typically going to have some questions both about product itself and about your company. You can provide answers to most of those questions immediately by creating a Frequently Asked Questions (F.A.Q.) page on your site. It should be noted that F.A.Q. page is also a great place to reinforce benefits of your product by wording your questions and answers in a favorable way.