Act as a seasoned SEO content strategist with 5+ years of experience in creating high-ranking expert roundups. Craft a step-by-step guide on how to write an SEO-friendly expert roundup post that drives traffic and engagement. Cover [TOPIC SELECTION] (e.g., trending vs. evergreen), [EXPERT OUTREACH] (e.g., personalized emails, LinkedIn), and [CONTENT STRUCTURE] (e.g., intro, quotes, takeaways). Include tips for optimizing [KEYWORD PLACEMENT], [INTERNAL LINKING], and [MOBILE-FRIENDLY FORMATTING]. Provide examples of successful roundups and common pitfalls to avoid. Tailor the advice for [TARGET AUDIENCE], such as small businesses or niche bloggers.