Share your gameplan with the client

From the first day of the project, start writing a document called a "gameplan". Share the gameplan with your client, no matter how general and inadequate this gameplan is, by granting the client read-only access to this document. The gameplan will then develop on a day-to-day basis. This document will simultanously serve as a project log and a historic document, describing every move of the SEO project.

Google Documents is great for sharing documents.