Warren Buffett has shared countless investing insights over the decades.
But one simple rule stands above the rest: buy wonderful ASX shares at fair prices.
It sounds straightforward. Yet most investors do the opposite. They chase cheap ASX shares, trade frequently, or panic during market pullbacks. Buffett's edge hasn't come from complexity. It has come from discipline.
Here's how that rule could transform an ASX share portfolio.

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Focus on wonderful ASX shares, not cheap
Warren Buffett doesn't look for the lowest price-to-earnings ratio in the market. He looks for sustainable competitive advantages.
On the ASX, that might include companies like ResMed Inc. (ASX: RMD), which operates in sleep disorder treatment with high barriers to entry. Or REA Group Ltd (ASX: REA), which dominates online property listings with powerful network effects.
These shares are rarely the cheapest on traditional valuation metrics. But their competitive positions allow them to grow earnings consistently over long periods.
Buffett would argue that paying a fair price for quality beats buying average businesses at bargain prices.
Think in decades, not quarters
Another part of Warren Buffett's rule is time horizon.
If you buy a wonderful business, the intention should be to hold it. That long-term mindset changes behaviour. You become less concerned about short-term volatility and more focused on whether the company is strengthening its competitive position.
Take ResMed. Demand for sleep and respiratory care is supported by demographic trends that will likely persist for decades. Over a long horizon, those drivers matter far more than short-term share price swings.
Let compounding work quietly
The real power of Buffett's rule lies in compounding.
When a business consistently reinvests profits at high returns on capital, earnings grow. When earnings grow, the share price tends to follow over time.
That's how Berkshire Hathaway (NYSE: BRK.B) became one of the world's most successful investment vehicles. Not through constant trading, but through owning great businesses and letting time amplify returns.
An ASX share portfolio built around high-quality compounders can operate the same way.
The transformation
Applying Buffett's rule doesn't require outlandish strategies.
It just means being selective. It means resisting the urge to constantly rotate. And it means prioritising business quality over short-term price movements.
Over time, that shift in mindset, from trading to owning, can be the difference between average returns and truly transformative wealth creation.