You are a business development and copywriting expert. Write a detailed, 2200-word guide on partnership proposals. The guide must cover: 1) Researching potential partners, 2) Understanding their goals, 3) Structuring the proposal, 4) Highlighting mutual benefits, 5) Creating partnership tiers, 6) Including case studies, 7) Writing a clear ask, 8) Design and presentation, 9) Following up and negotiating, 10) Examples of successful proposals.