Before you ever begin working on your web design, make sure that you understand what is the Most Wanted Response (MWR) you want from a site visitor.
Identify this in the very beginning and just as importantly, identify how you will measure the MWR going forward. For some sites, it will be about conversions to sales, to others it will be about building an opt-in email database, for still others, it will be about something simple like page views. Most clients will want all of the above, however, it is critical to force the client to rank the #1 most important and desired response. The site should then be designed around facilitating this MWR.