Act as an experienced SEO content strategist with 5+ years of expertise in creating high-ranking roundup posts. Your task is to outline a step-by-step guide for writing an SEO-optimized roundup post that ranks for [TARGET KEYWORD] and engages [TARGET AUDIENCE]. Include the following elements: 1) How to select [TOPIC/INDUSTRY]-relevant contributors or sources, 2) Best practices for structuring the post with [NUMBER] expert quotes or examples, and 3) On-page SEO techniques like [SPECIFIC HEADER TAGS] and internal linking strategies. Also explain how to balance readability with keyword density, and provide a checklist for optimizing meta titles/descriptions. Format the response as a actionable tutorial with bullet points and concrete examples.