A clear request names the action, supplies enough reason or context, and gives a realistic time frame. Politeness comes from respectful wording and reasonable expectations—not from making the request so indirect that the reader cannot tell what you need.
A useful follow-up restores context, states the current status, and explains why the response matters now. Avoid blame. If a deadline is at risk, name the consequence and propose an option: a new date, a smaller deliverable, a different owner, or a brief conversation to remove the blocker.