One of the best (and least stressful) investing strategies is to buy great businesses at great prices and hold them forever. Sticking to the strategy is simple but not easy.

How do you identify a great business? What's a good price, especially when your holding period is a lifetime? Investing may seem daunting, but individual investors can find the best stocks to own by putting in the time and doing the work with high-quality research.

We recently asked three contributors at The Motley Fool for their best growth stocks to buy and hold forever. Here's why they chose NextEra Energy Partners (NYSE:NEP), Mastercard (NYSE:MA), and Amazon (NASDAQ:AMZN).

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A solid renewable energy yieldco

Maxx Chatsko (NextEra Energy Partners): Thanks to economic and geographic factors, the United States is the best market in the world for renewable-energy assets. On average, the lowest-cost electricity comes from onshore wind turbines, while solar is the third-cheapest source of power. As technology improves and the supporting industrial ecosystem blossoms in the coming years and decades, the United States will remain a safe haven for clean-power companies.

That bodes well for NextEra Energy Partners, a fast-growing renewable-energy yieldco building a portfolio of wind and solar power assets in the United States. It benefits from a close relationship with its parent NextEra Energy, which also is the world's largest publicly traded utility by market cap and produces more electricity from wind and solar than any other company in the world. As the parent builds out its 40,000-megawatt backlog of projects through its power-generation subsidiary, NextEra Energy Resources, it will inevitably offer first dibs to the yieldco.

The relationship essentially provides NextEra Energy Partners the right of first refusal to the world's most enviable pipeline of renewable-energy projects. It recently completed a $1.3 billion transaction with NextEra Energy Resources that added 11 renewable-power plants to its portfolio, which now boasts 4,100 megawatts of wind power and 600 megawatts of solar. As a result, the yieldco expected to exit 2018 with an annual run rate of $1 billion in adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) and $360 million in cash available for distribution after debt payments.

Investors can expect similar transactions to occur in the future, especially given the enormous renewable-energy project backlog in the NextEra Energy universe. That promises to allow NextEra Energy Partners to continue beating the S&P 500 (shares have bested the total return of the index by 15% since debuting in 2014) and continue paying a healthy dividend (now yielding 4.3%).

Management even thinks the stock can deliver average total returns of at least 16% per year through 2023. A long-overdue recession may have something to say about that, but either way, this business is well-positioned for long-term growth.

Check out the latest NextEra Energy Partners earnings call transcript.

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A top-quality play in a growing industry

Neha Chamaria (Mastercard): Duopoly in a high potential industry, a highly profitable business, an enviable operational track record, a visionary leader, proven commitment to shareholders, and an eye into the future -- Mastercard is all this and more. Not surprisingly, it's one stock I'd want to hold for decades and maybe even pass on to the next generation.

Chances are, you already own a Mastercard-branded card. What you may not know, though, is that every time you swipe its card to make a purchase, Mastercard earns a fee. With nearly 2.5 billion cards in circulation across the globe, those fees rack up big sums of money for the company.

The best part is that Mastercard's an asset-light business as it simply facilitates transactions between parties like banks and financial institutions, merchants, and consumers over its payments-processing network. That largely explains why Mastercard can consistently earn operating margins north of 50%.

The company's reach is smaller than that of rival Visa's, but there's plenty of room for both companies to grow massively in the coming years for several reasons. The most important one is that plastic money and digital payments are just picking up steam in some of the largest nations in the world such as India, which is driven largely by e-commerce. It's a powerful trend that should only grow with time.

Meanwhile, Mastercard also is investing in advanced technologies like blockchain, while strengthening its existing payments network. All of these moves should make Mastercard a key beneficiary of the world's cashless drive and its stock a solid investment for decades to come.

Check out the latest Mastercard earnings call transcript.

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Slightly down but nowhere near out

Chris Neiger (Amazon): Sure, Amazon's share price has taken a hit over the past three months. As of this writing, the company's stock has fallen about 14% since the beginning of October. But even if the company's shares continue to fall this year, there are plenty of reasons to buy and hold this stock for decades to come. Here are just a few.

First, Amazon is a cloud-computing juggernaut. The company's Amazon Web Services (AWS) holds 34% of the public cloud-computing market share right now -- far ahead of its largest rival Microsoft, with 14% -- and continues to benefit from this growing trend.

In the most recent quarter, Amazon earned $2.07 billion in operating profit from AWS, up 77% year over year, making it slightly more profitable than the company's U.S. e-commerce segment. Right now, the public cloud market is worth $221 billion, and by 2021, it'll jump to $302 billion. Amazon's lead is solidified in this space, and no company is better positioned to benefit from growth in the cloud-computing market.

Second, the company is well on its way to becoming an advertising powerhouse in the U.S. Amazon is now the third-largest digital-advertising company behind Facebook and Alphabet's Google and doesn't need to beat these rivals to benefit. Instead, investors should see Amazon's ad sales as icing on the company's revenue cake. With Amazon owning the largest e-commerce platform in the U.S., companies always will want to advertise their products on Amazon's site. As a bonus, Amazon is far less likely to get involved in the same advertising scandals that some of its competitors are dealing with.

There are plenty of other reasons why Amazon makes a great long-term bet for investors. The company's focus on using machine learning in nearly every aspect of its businesses, its focus on smart assistants and Echo devices, and its 100 million Prime memberships all help make the company a compelling buy. With the company dominating its current market and quickly expanding into new ones, Amazon looks like an an excellent investment for decades to come.

Check out the latest Amazon earnings call transcript.