Lessons Learned: The product manager's lament

Switch the spec process from push to pull. Start with a one-page spec, no more. Then, let the team ask questions of the product manager whenever they need clarification. In exchange, the team agrees to show each piece of working code to the product manager for his approval. They’ll find points of disagreement much faster, and resolve them in realtime. Plus, the team will get better and better at interpreting the concise specs that only have to be written once. (Eventually, they may abolish specs altogether)
(Link: Lessons Learned: The product manager’s lament)