Billionaire entrepreneur John Paul DeJoria shares his best advice for managers

There was a time in John Paul DeJoria's early 20s when he was living out of his car and picking up discarded bottles to cash in for a few bucks.

Today, he's 71 years old and has an estimated net worth of $2.9 billion, largely due to the success of his companies John Paul Mitchell Systems hair care and Patrón tequila.

After his businesses hit their stride in 1999, the CIA called DeJoria in to assist the organization with a management training program. He tells Business Insider that he has also taught his principles at the FBI.

His main message: Operate on fewer moving parts to move efficiently, and personally acknowledge your employees to create unity.

While DeJoria has admitted that it was difficult getting the CIA to reduce bureaucracy, he says his main approach to business leadership involves cutting out middle managers.

"A lot of people are just bogged down with middle management and don't give other managers the opportunity to make decisions," he says.

He explains that he also considers it crucial to keep praise public and criticism private.

"Whenever someone does a good job, praise them loudly in front of as many people, whether it's one person or 50, as you possibly can," he says. "Whenever you have to reprimand somebody, do it one-on-one behind closed doors so nobody hears you."

And after pointing out what they did wrong, DeJoria says, it is crucial to both explain to them how to do their task correctly and acknowledge something that they're doing right so that "they leave with a good feeling."

DeJoria says one of his favorite books is Dale Carnegie's 1936 classic "How to Win Friends & Influence People," which says the best leaders understand that "abilities wither under criticism" and "blossom under encouragement."

To DeJoria, managers need "to let their people know they're loved" if they want to have a fully engaged and motivated workforce.