Legendary investor Warren Buffett is so revered and his advice is considered so valuable that a private steak lunch with him fetched $19 million at a charity auction last year.

The annual meetings of his company Berkshire Hathaway also give shareholders the opportunity to pick his brain on a wide range of topics.

Don’t miss

• Commercial real estate has outperformed the S&P 500 over 25 years. Here's how to diversify your portfolio without the headache of being a landlord

• Rising prices are throwing off Americans' retirement plans — here's how to get your savings back on track

• 'A natural way to diversify': Janet Yellen now says Americans should expect a decline in the USD as the world's reserve currency — 3 ways you can prepare

However, one investor who attended the conference in 1999 cut right to the chase. “Mr. Buffett, how do I make $30 billion?” he asked.

As always, the Oracle of Omaha conveyed complicated theories in simple terms. Here are the three crucial rules that helped the 93-year-old accumulate a massive fortune and could help ordinary investors too.

Start young

Buffett’s best advice for investors is to get started as early as possible. He has a simple metaphor to explain his wealth-building strategy. “We started with a little snowball on top of a very tall hill,” he said. “We started at a very early age in rolling the snowball down, and of course, the nature of compound interest is that it behaves like a snowball.”

Indeed, the length of Buffett’s career is a key piece of his enormous wealth. He bought his first stock at the age of 11. He’s now 93 years old and still actively investing. In fact, the majority of Buffett’s wealth was accumulated after he turned 65. In 1999, his net worth was just $30 billion. Today, it’s nearly four times greater at $116 billion, as per Bloomberg.

Staying invested over a long period of time is crucial. Ordinary investors can best harness the power of compounding by starting as early as possible.

Search for small companies

Buffett said that if he were starting again today with $10,000, he would focus first on small businesses. “I probably would be focusing on smaller companies because I would be working with smaller sums and there’s more chance that something is overlooked in that arena,” he said at the shareholder meeting.

In his early days, the billionaire investor focused on extremely small companies that would be considered small-caps. He bought a tiny furniture company in Nebraska in 1983 when it was still expanding across state lines. He acquired See’s Candies when it made just $4 million in annual profits in 1972.