At some point in life, everybody has to take a start on a new project, whether that's school, a hobby, or a new job or career. Everybody is a beginner at some point.

And the biggest mistake you can make is not seeking advice from the right sources.

That's according to Jim Wendler, a former college football player who turned to power-lifting and business. He squats over 1,000 pounds in competition, and his 5/3/1 program for weightlifting has been taught to millions of athletes around the country. His books have sold over 547,000 copies.

"I tell people all the time: The biggest problem with beginners is they listen to other beginners," Wendler tells CNBC.