As sales expert Perry Marshall puts it, there are three steps to selling anything: Traffic, conversion, and economics. These are the "cornerstones" of sales and marketing, he says.

"You get the traffic, you convert the traffic, you sell the traffic, then you take your money and you reinvest it in more traffic," says Marshall, author of 80/20 Sales and Marketing (Entrepreneur Press). "If you can make the process profitable then it goes around and around and your company grows bigger."

The most important element of the process is the economics, Marshall says. Can you reach your customers affordably? Could they be willing to give you even more money than they already give you now? 

In this video, Marshall explains.

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