Trump expert Tony Schwartz reveals ‘all you need to know’ about the president
Tony Schwartz co-wrote the 1987 book 'The Art of the Deal' with Donald Trump

The co-author of the president's 1987 autobiography Trump: The Art of the Deal on Friday revealed "all you need to know" about the commander-in-chief.

Tony Schwartz offered advice on how to respond to Trump as his behavior becomes even more erratic.

"As we all know, Trump is shameless and compulsive liar. Here's the solution: ignore everything he says -- everything," Schwartz counseled.

"Don't waste any energy in outrage," he continued.

"Just know nothing he says is ever true," Schwartz said. "That's all you need to know."