When eyeglasses company Warby Parker launched in 2010, its founders had invested their life savings in three main areas: their glasses, their website and, very important, a public relations team, says Neil Blumenthal. 

"We knew that you only have one shot to launch a fashion brand," he says. 

Blumenthal had his sights set on Vogue and GQ magazines, where he wanted his company's name to debut. The PR team managed to work Warby Parker into the pages of February issues that year, and the result was better than anyone could have expected.

"We ended up hitting our first-year sales targets in three weeks and were just on this crazy, crazy ride," Blumenthal recalls.

Ever since, Warby Parker has managed to turn these press-triggered sales spikes into sustained growth, which Blumenthal attributes almost entirely to word of mouth.

"Everybody's looking for that tidbit to talk about at the dinner table. What is it? For us it was the $95 price point," he explains. "It was the innovative business model of our home-try-on program."

Blumenthal says that more than 50 percent of Warby Parker's sales are driven by word of mouth, and that's something the company wants to continue.

"Certainly of any form of marketing it's got the highest return on investment because it doesn't cost you much," he points out.

For more on the power of positive press, check out the video below.