Act as a certified financial advisor with 10+ years of experience in passive investing. Provide a detailed guide on the best ways to invest in ETFs, covering [TIME_HORIZON], [RISK_TOLERANCE], and [INVESTMENT_GOAL]. Include strategies like dollar-cost averaging, sector diversification, and tax-efficient ETFs. Explain how to evaluate expense ratios, liquidity, and tracking error. Tailor the advice for [AGE_GROUP] investors looking to build long-term wealth. Use real-world examples and avoid overly complex jargon.