Actor-turned-entrepreneur Ashton Kutcher shares his single best piece of investing advice

If you know Ashton Kutcher primarily from films and television, it may surprise you to hear that the 38-year-old actor has also quietly built a media empire, cofounded a human-rights organization, and appeared as a guest Shark on "Shark Tank."

He's also built an impressive $250 million portfolio, investing in tech companies such as Skype, Spotify, Uber, and Foursquare, and was recently on the cover of Forbes magazine, featured as one of tech's top investors.

On Chelsea Handler's new Netflix talk show "Chelsea," Kutcher offered up his best investment advice:

Invest in the things that you know. If you drink beer all the time - if you go to microbreweries and you try all kinds of them - you probably know which ones are the best, and my advice is always to invest in what you know.

If you're a stock boy in a grocery store and you see something flying off the shelf, find out who made it. Find out why it's flying off the shelf. Do the investigation necessary to know whether or not it's something that is going to have ultimate value.

He's not the only successful entrepreneur to preach this advice.

Josh Altman, self-made millionaire and the star of Bravo's "Million Dollar Listing Los Angeles," said essentially the same thing when asked about his best investing advice: "Invest in something that you know."

For him, that means real estate. If he's ever investing outside of the real estate realm, "It's got to be something that I use," he says. "If I like Colgate toothpaste, then I'm going to invest in Colgate. I don't invest in things that I don't use. That's my investment strategy personally, and it's worked for me."