Wireframes - Functionality NOT Layout
So...what do you want the site to do again? Design is the SECOND more important element to any website. The first is the objective. There are usually two. A wireframe should cover the functionality which should exist. Tools handy for doing this are Microsoft Visio (for Microsoft users) and Freemind for the Open Source inclined.
Whatever you choose to use, do your designer a favor and be explict in the primary and secondary objectives of the site. Don't try and design unless you're a designer.