Gregory Cuneo learned to be tough and smart in his schoolyard in Bensonhurst. Now that he’s one of the biggest general contractors in the construction business, those lessons are coming handy.

“This is a tough business,” Mr. Cuneo said over lunch. “At any given time, I have 15 projects going on. I typically hire 20 subcontractors for most high-rises I work on – that’s nearly 300 people right there for every project. I’ve got to deal with 30 unions – those guys are real colorful – and I’ve got to deal with builders and architects. This is a very macho industry. What I learned in Brooklyn is proving very useful.”

And what exactly did he pick up in his youth?

“That you’ve got to be tough – but not too tough, otherwise you’ll antagonize people,” said the 47-year-old chairman of HRH Construction. “That you’ve got to be smart – but not show off. In Bensonhurst, I learned that these tactics were the best way to deal with schoolyard bullies.”

There are those who might say that Mr. Cuneo’s mentor and patron, Donald Trump, is the biggest bully of them all. But Mr. Cuneo isn’t one of them.

“Donald gave me a big boost early in my career,” Mr. Cuneo said. “And I’ll always be grateful to him for that.”

Mr. Trump calls Mr. Cuneo “my original apprentice.”

Mr. Trump was so impressed that he now designates Mr. Cuneo as the general contractor on all his construction projects. These assignments, plus other contracts in the tristate area, add up to a $500 million business annually. Not bad for a guy who failed engineering courses at the State University of New York at Oneonta.

His relationship with Mr. Trump began not long after Mr. Cuneo did some work for Mr. Trump’s late father, Fred, who was a noted builder in Brooklyn and Queens. Mr. Cuneo was invited by Andrew Weiss of the Trump Organization to meet with the younger Trump at his Fifth Avenue headquarters. Mr. Cuneo’s friends hired a limousine to transport him.

“I was as nervous as nervous can be,” Mr. Cuneo said. “After all, this was Donald Trump.”

It was Mr. Trump who did most of the talking for nearly an hour. At the end of the meeting, the conversation went something like this:

Mr. Trump: “Greg, I’m going to make you a millionaire.”

Mr. Cuneo: “Donald, that’s a good idea.”

That, of course, is precisely what happened in due course. But it wasn’t an easy ride to riches for Mr. Cuneo.

“When I first got into the construction industry, I would think, ‘Hey, if I got a $30,000 paycheck, then I was made,’ ” Mr. Cuneo said.

Those modest ambitions swirled in his mind when he worked for a Long Island company, Afgo Engineering. He got a job there at the recommendation of his cousin, Ronnie Fregara, who was already employed at Afgo.

Afgo’s owner, Burt Reyer, was struck by Mr. Cuneo’s enthusiasm and eagerness to learn rudimentary things such as making job estimates. He took Mr. Cuneo under his wing, and the pupil’s ambitions began to soar.

“Four people have been the biggest influences in my life – my parents, Angelo and Joan, Burt Reyer, and Donald Trump,” Mr. Cuneo said.

His father was a social worker who also helped out at a senior citizens center. His mother was a schoolteacher. Mr. Cuneo said they taught him and his three sisters the importance of respecting other people’s opinions and values, even if they diverged from his own.

Mr. Reyer’s mentorship included dispatching Mr. Cuneo to supervise construction projects. At one such project – Trump Plaza at 100 Central Park South, where Mr. Cuneo was project manager – he came into contact with the Trump Organization.

Afgo was bought by JWP, which is now Emcor. Mr. Cuneo became disenchanted with what he would only characterize as “the management’s questionable style.” He decided that he’d gained enough experience in construction to start his own business.

It was in his grandmother’s home in Brooklyn – the only “office” he could afford – that Mr. Cuneo launched Mechanical Associates. Tapping the contacts he’d made in previous jobs, he steadily secured assignments and wound up taking the company public in 1995. Mr. Cuneo raised $16 million.

He became a sought-after player in New York’s construction business, currently estimated to be about $40 billion annually. General contractors are responsible for such things as wiring buildings and finishing the insides. Eventually, he bought HRH Construction. Business began to boom after he met Mr.Trump.

So what explains his growing success since that fateful encounter?

“I always say that it’s luck, but my wife says it’s hard work,” Mr. Cuneo said. “I get along very well with people. I’m very honest and sincere. I’m not a chairman who spends his time on golf courses. I’m usually at project sites. I reserve my ego for those occasions when my young son pitches in ball games. I never forget that my parents gave me values, that Burt Reyer taught me business fundamentals, and that Donald Trump gave me the opportunity. And I have a major rule when doing business: If something smells bad or looks bad, you just don’t do business with bad guys.”

How does he deal with alleged mobsters who’re reputed to flex their muscle in the construction business?

“Schoolyard rules,” Mr. Cuneo said.