File signed agreements, keep order receipts, bundle handoffs. Every one is ready to run, and you can adjust it in plain language.
Email the current creative proof and note the revision sent.
Your reviewer gets the current image or PDF and a clear question. Your review card shows which revision you sent.
Keep each artwork decision with the exact proof reviewed.
Your review cards show who made a proof decision and which file they saw. The reply time stays with the decision.