In 1955, Eli Broad's story wasn't too different from those of many Americans. He graduated from a good college, got married, and was working as a CPA and assistant professor. 

By 1957, he co-founded what would become his first Fortune 500 Company, KB Home, and by the late 1980s he repeated the feat with insurer SunAmerica, making him the first person to found two Fortune 500 companies in different industries. Today, his estimated net worth stands at $6.9 billion .  

Between 1955 and 1957, nothing about Broad's personality or mental capacity changed. He wasn't bitten by a radioactive spider, and he didn't take any special pills to enhance his brain power (that we know of). Broad did, however, become an expert.

What his story demonstrates is by dedicating all of your energy to becoming an expert in one industry, rather than attempting to understand every sector, is the key to finding great opportunities. 

1. Become an expert
Working as a CPA, Broad wanted more -- "more money and more excitement" -- and he believed real estate was where he would find it. Like many of today's job seekers, however, Broad's attempts to land a career in homebuilding were denied for lack of experience. 

Unfazed by his lack of success, Broad decided to take a leap of faith by starting his own homebuilding company. He read every industry magazine he could get his hands on, studied homebuilders for what worked and what inefficiencies he could improve upon, and partnered with experienced real estate expert Donald Kaufman -- the "K" in KB Homes. 

He was relentless in his effort to expand his expertise, and that was the key.

2. Ask the right questions
Many investors focus primarily on specific companies, or stocks, but that could be a mistake. Your focus should start with gaining a vast knowledge of an industry, because when you understand an industry, you start asking big questions -- the questions that go beyond quarter-to-quarter analysis and cut to the core of a company's future. 

As Broad's expertise grew, he saw one very important macro trend emerging. A whole new generation of homeowners, baby boomers' parents, were leaving the cities and flocking to the suburbs. Broad believed that if he could improve on the inefficiencies he saw, he could lower the cost of housing enough to where homeowners' mortgage payments would cost the same as renting an apartment.

One of the more notable ways Broad was able to make that happen was by building homes without a basement. That may not seem revolutionary now, but it was fairly radical for the time. 

The idea, along with Broad's keen eye for finances, helped keep housing prices down, and the company exploded, expanding from Detroit to Arizona, then California, and then France, all within 10 years of the company's founding. KB Homes went public in 1986. 

3. Diversify
Broad wasn't satisfied. He understood that the housing market is cyclical, and he wanted to generate more consistent returns. So Broad turned to one of the oldest investing strategies in the book: "diversification," the process of reducing risk by investing in multiple market sectors and investment vehicles. 

However, when you truly understand what makes an industry tick, you can diversify with a purpose. Broad realized that real estate growth is strongest during lower-interest-rate environments and economic boom times. To smooth out volatility, he needed a business that could perform well in less favorable economic climates, and insurance was the perfect fit. 

Insurance is an essential. In good times or bad, consumers and businesses need to be covered against risk. Also, when interest rates rise, insurers can invest the premiums they collect from customers at higher rates, which generates greater investment income. 

Broad would build the company's insurance arm into a powerhouse provider of retirement savings plans, such as annuities. Broad split the company up in 1989 and created two separate publicly traded companies -- KB Homes and SunAmerica. Broad sold SunAmerica to American International Group in 1999 for $18 billion. 

The last word
Broad's passion for real estate and the expertise he developed allowed him to understand and take advantage of two major trends: the need for affordable housing in the 1960s and the need for that same population to plan for retirement. 

What trends will dominate the next decade in tech, health, energy, finance, and other sectors? I believe that by becoming an expert in one industry, rather than spreading your focus too thin, investors can spot hidden gems primed to take advantage of tomorrow's economy.