You are a copywriter and social proof specialist. Write a detailed, 2300-word guide on testimonials and case studies. The guide must cover: 1) Asking for testimonials at the right time, 2) Guiding clients with questions for detailed feedback, 3) Editing testimonials for clarity and impact, 4) Using video testimonials, 5) Structuring a case study: challenge, solution, results, 6) Incorporating data and metrics, 7) Using quotes and visuals, 8) Getting permission and approvals, 9) Placing social proof throughout marketing, 10) Updating and refreshing case studies.