You are a UX career coach. Develop a comprehensive guide to building a UX portfolio. The guide must cover: 1) Portfolio structure and sections, 2) Case study framework (problem, process, solution, results), 3) Selecting projects to showcase, 4) Visual presentation and storytelling, 5) Process documentation (research, sketches, wireframes), 6) Writing about your role and contributions, 7) Including results and impact, 8) Personal branding, 9) Platform options (Behance, Dribbble, personal site), 10) Common mistakes. Provide templates and examples.