zara shopperAndrea Comas/ReutersPeople walk past a Zara store in Madrid
Teens are demanding customers.
Earlier this month, Neil Saunders, CEO of consulting firm Conlumino, told Business Insider the three things that retailers can do to win the hearts and wallets of teens.
One in particular stands out.
"Constant newness to engage and stimulate is one of" the ways to win over teens, Saunders told Business Insider via email.
Another way of phrasing that? Fast fashion is key.
Fast fashion has transformed the way teens (and adults) shop for apparel. Stores like Zara churn out runway-inspired styles at rapid fire speeds at affordable prices. Zara, for instance, even recently produced Yeezy knockoffs, though the line provoked some disdain of some consumers.
Zara is arguably the beacon of fast fashion, as it consistently updates its collections and stocks very little, giving consumers a new reason to come back every time. The company avoids fashion misfires, thanks to its data center that tracks sales data and customer feedback.
Zara's smart business model should have other retailers shaking in their boots.
"We believe that Inditex has the best business model in apparel and expect Inditex to deliver double-digit earnings growth per year over the next five years," Bernstein analysts wrote, according to The Wall Street Journal. 
Additionally, the other ways to engage teens, Saunders explained, also involve strategies that incidentally have helped Zara beat retailers.
"A good digital strategy in terms of marketing and shopping is another," he wrote. Zara has an excellent Instagram strategy. Shoppers see new apparel on Instagram and want it immediately; this works in tandem with Zara's in-store strategy of swiftly bringing in styles.
Other retailers — even those who don't target teens like Banana Republic — have taken cues from this model, by putting runway styles on sale immediately.
But Banana Republic doesn't have Zara's sweet price point, and Saunders said that "value for money is definitely a third: teens have so many things they want to buy so what they have to spend on particular items is often constrained." Zara is undoubtedly known for its affordable prices, as are other fast fashion behemoths, like Forever 21 and H&M.
But the latter isn't particularly new; when teens have money, they often want to get the most they can.
"I think back to when I was young," Gabriella Santaniello, founder of consulting firm A Line Partners told Business Insider recently, "if you had 50 dollars, you wanted to buy as many units as possible. 'How much can I get for 50 dollars?'"
But while stores like Zara and Forever 21 are built on the model of selling cheap, dispensable apparel, other retailers who have been around before the proliferation of fast fashion are not.
"And at some points, it's not sustainable for these larger retailers who have hundreds of stores to provide [a] product that's that cheap," Santaniello said.