One of the best ways to help clients prioritize information and set a site strategy to help visualize the site architecture. This can be done in a huge variety of ways, but often I use two lenses to communicate how users will use a proposed site.
Site maps are a great way to illustrate site architecture (pages, processes or contexts). User flows show how a use case or user task will be completed. Depending on the project, one or both of these architecture deliverables may be helpful.
The goal of these documents is to walk stakeholders and team members through an experience without having to design the entire experience to do so. I often find that spending a little time up front laying out a map or flow will both highlight potential confusion and gaps as well as solve many problems before they pop up.