Mark Cuban uses these 3 fundamental rules for running all his businesses

"Shark Tank" star and billionaire owner of the Dallas Mavericks Mark Cuban always has his hands in a wide variety of businesses.

Throughout his career, he's made over 120 investments, from large companies like Landmark Theatres to his Three Commas apparel line.

For all of the businesses he's been a part of, he's developed a set of "rules that have been almost infallible," he wrote in his 2013 book "How to Win at the Sport of Business."

Below, Business Insider has summarized the three he's used "religiously."