Wireframes
Your wireframe is really the "web version" of your finalised site structure and concept grid with your clients or dummy content inserted into each page.
It should all be in Grays, Blacks and Whites so your client doesn't sit there during the scripted walkthrough debating wether the icons should be in cornflower blue and focuses on the important thing, the content. However, in saying that you might want to add some text here and there that says "Logo goes here" or something similar, just so the client knows that their branding will be there.
Jeff Lash has an article at Digital Web with the great idea of creating wireframes in XHTML/CSS, that way changes can be easily made and incorporated into the colour version later in the project. Gabe Zentall has been nice enough to share with everyone his User Interface Library for prototypes and user interface schematics if you plan to use a paper based or PowerPoint type presentation, these are an excellent aid.
