Warren Buffett's wealth largely comes from compounding interest after age 65. He started investing young and advises starting early, even with small amounts. Compounding accumulates interest on interest, growing wealth significantly over time. Don't try to time the market; instead, stay invested and ride out market fluctuations. Set up automated investments and have a clear goal in mind to stay motivated. Simple strategies like investing in an S&P 500 index fund can also be effective.