Ultimately, your idea is "only as good as the marketplace is willing to accept, consumers are willing to buy, and there's margin to be made," he said.
If you're trying to get people to invest in your idea and no one is biting — or if you're advertising and people aren't calling — that's a warning sign, Lemonis said. "It's kind of common sense. If people don't raise their hand wanting it, then maybe no one really wants it."
The best way to evaluate your idea's potential is to ask people what they think — but don't take the easy route and just ask your friends and family. As "Shark Tank" investor Barbara Corcoran told Business Insider, oftentimes they love you too much to be objective.
Seek unbiased responses, she advised. If the reactions are indifferent or negative, go back to the drawing board and strengthen your idea. If they love it, Corcoran said, "tell them you'll take an order right then and there, and see if they'll hand over the money!"
CNBC's "The Profit" airs Tuesdays at 10 p.m. EDT.