Luke Wroblewski's book on web form design starts by telling us to build things from the outside in. He does a great job of explaining the merits of user centric, task focused design by describing what it isn't.
Book: Web Form Design: Filling in the Blanks
What should we include in our forms? What should we skip? Where should the submit button go? Where should I place my labels?
How you answer these questions greatly impacts interaction with your site. Luke's book, provides the research you need to answer these and other questions. The result, less user frustration.
Amazon sells copies of Web Form Design: Filling in the Blanks for $36 + shipping.