The power of Millennials is no joke: They're now a leading group of consumers, at 75 million strong. With roughly $200M in annual buying power and a strong voice on social media, discerning (and some say demanding) Millennials dictate not just what happens with their wallets, but also often with national conversations.

So what Millennials want--and expect--from brands is worth grasping if you want to market to them successfully.

Ross Paquette, founder and CEO of tech startup Maropost, has built a business around customer input--improving and innovating based on customer needs, many of whom are Millennials. While the company began as an email service provider, Maropost grew to span cross-channel marketing, total sales cycle management, and everything in between--largely through customer feedback.

For Paquette, it all comes down to one thing: "Customers are more than just the people buying from you--or at least they should be. Your success depends on taking company-customer relationships from transactions to connections."

Your success depends not on transactions, but on connections.

The old-school version of business was to see customers as passive recipients of things, whether that thing was an ad or a product someone bought in a grocery store. Before the advent of social media, for example, it was nearly impossible for a big (or little) brand to have any kind of dialogue with consumers, let alone a public one like those that now regularly take place on Twitter, Facebook, and Instagram.

Now, taking your business to the next level requires seeing customers in a fundamentally different way. They're not passive recipients; they're active participants--a fact that can be either intimidating or galvanizing, depending on how you look at it.

According to recent research by TotalRetail, 45 percent of Millennials expect more engaging experiences with brands than with retailers. In other words, they expect brands to build relationships with them, to listen to them, and to engage with them. They want to be part of the innovative process (especially if something isn't working for them).

For Paquette, this approach was a founding principle of the startup: "Customer-first innovation directs every decision we make--everything we create, we create for our customers." It's not just lip service, either. At Maropost, everything from feature tweaks to entire platforms have been created based directly on customer feedback.

Obviously this requires investing energy into building the right kind of structure: you need a robust feedback loop that goes from customers, to customer support, to development, and back to customers.

It's worth investing that energy, though. "We've been able to build out our capabilities to a level you only see at much larger companies," says Paquette, "and we're winning against some of the industry's biggest players."

In fact, Maropost is now a leading enterprise digital marketing startup, with customers that include Rolling Stone and Mercedes-Benz. Many of their key customer decision-makers are Millennials, and they keep in close touch with them.

In the past, one-way relationships were the norm. You made the sale and were done. Few companies were interested in nurturing a relationship. Now, not only does that attitude not fly, but it constitutes a missed opportunity.

When companies are committed to true partnership with their customers ... it shows. They prioritize smart feedback loops that connect people in social media with people in customer support with the development team. The things customers say (and Millennials don't tend to hold back) are crucial--and smart companies know that they've got to make sure those comments aren't wasted.

Treating customers as collaborators also ensures you're answering real business needs--instead of operating in an echo chamber. When you collaborate directly with the people using your product and consistently seek out their feedback (instead of just assuming they'll tell you), you don't lose sight of what they need. It's right there, in their words. 

Obviously not every comment is worth a feature update. But wise is the company that has a strategy in place to capture those that are--and who actively, consistently, and intentionally focus on building connections rather than transactions.