In comes User Stories, a really clever way to define exactly what the users need and why, without makes assumptions about how to make it happen.
User stories are written like this
As a <type of user>, I want <some goal> so that <some reason>.
As a user I want to find contact information so that I can get in touch with the organisation.
I have found user stories really helpful, not only in cases of development, but also for design decisions. It is done in a language that the client can understand, and the developer or designer can interpret, without having to read between the lines.