"Shark Tank" investor Kevin O'Leary cares most about making money, and that starts with getting customers to open their wallets. 

Last weekend, ABC aired a 20/20 special in which O'Leary (a.k.a. "Mr. Wonderful") taught aspiring entrepreneurs the tricks of the trade. 

Three college seniors were selected to hit the New York City streets and sell "Wicked Good Cupcakes," a product that recently secured funding on "Shark Tank."

Before they set off, O'Leary schooled them on his five most important principles of effective salesmanship:

1. Walk the walk. 

"Good salesmen and [sales]women understand it's their destiny to be a salesperson and to be great," O'Leary said. "It has to be there, all the time, 24/7, no chink in that argument."

2. Feel the love.

"You have to love the product you're selling," he said. "You have to have an emotional bond to it. It has to be oozing from every pore: This is the greatest product you have ever sold."

3. Make the perfect pitch.

"Don't dribble on; capture your audience immediately," O'Leary counseled. "Communicate your vision for why the product belongs in their hands--that's the perfect pitch." 

4. Be kind, not nice. 

"I don't trust nice people. I don't believe that someone can be nice all the time," he said. "Every product has its merits and its downsides. Don't lie about a product as if there are no problems at all. Create that bond, trust. That's paramount."

5. Be sticky, not gummy.

"Gummy people just keep going after the sale and wasting everybody's time," O'Leary said. "You have to make a decision, whether they're ultimately gonna' buy from you or not. As soon as you understand that they're not, don't waste your time. Cut them loose." 

O'Leary speaks from experience: He launched SoftKey Software Products from his basement, eventually acquiring The Learning Company and selling to the Mattel Toy Company for $4.2 billion in 1999. In 2008 he founded a mutual fund company, O'Leary Funds.

As O'Leary told his pupils, if your pitch isn't working, you've got to go back to the five principles of effective salesmanship and figure out which one you're not using. "Because if you're doing all of these, it works 100% of the time."

This story first appeared on Business Insider