This is easier said then done and often overlooked when designing a web site. I don't know how many sites I have come across in my almost ten years in this business that completely left their users out of the picture. The business may be worried about search engine visibility, design aesthetics or even actual web traffic but then wonder why the site does not convert well.

Yahoo Publisher Blog has a very good article on the subject of designing your web site with users in mind. And not just what "you think" they might want but conducting actual research. Here are a few excerpts.

Publishers face difficult decisions when designing their web sites. Often, design decisions are based on what publishers assume to be true about their end-users. However, to ensure the successful design of a web site, design decisions should be based on valid information, not assumptions, about users.

Most major Internet companies hire researchers to perform interviews and tests that captures feedback from end-users early in the web design process. Designers then incorporate the feedback gathered from users to make improvements to the interface—improvements that can increase the chance of a user taking the sort of action you want, such as clicking on one of your ads, or making the decision to buy one of your products. The earlier that users are involved in the design process, the better the chance your site will be a financial and creative success.

What’s vital, of course, is that you communicate with your users, and provide them with a channel through which to communicate with you. Offering an email address and soliciting feedback is probably the easiest and quickest method. Two other inexpensive ways to track what your users are thinking and saying include creating a blog that solicits comments from your users (such as this one), and developing a community forum of your own where your users can communicate with each other, as well as with you. You can glean a lot of information from monitoring these channels.

Using scenarios can be quite helpful for inspiring a design direction, but ideally you should validate your design decisions by performing usability testing. In this type of research, direct observations and feedback are gathered from actual users as they complete a series of assigned tasks while interacting with a prototype of the interface. Only then will you definitively know how well your proposed design meets the needs of your users.