LAS VEGAS -- In Las Vegas, if you're not new and fresh, you're old and boring. Casinos thrive on youthful energy and young executives flush with cash. Nightclubs buzz into the wee hours, chock full of hard-partying millennials, not stodgy Gen-Xers in desperate need of their beauty sleep.\nMarketers, too, need to reach millennials, but are they doing enough?\nLet the f-bombs fly and puppies roam\nAt Collision, an edgy tech event in Las Vegas this week, a panel of young marketers talked about wooing technically savvy, digitally driven millennials. Attendees poured into the room to catch the panel, called Marketing to Millennials, and panelists didn't disappoint. Social buzzwords rolled off their tongues, and they peppered their speech with f-bombs.\nIn fact, the panel echoed the event itself. Everything about Collision rings of youthful exuberance, from its Las Vegas venue of giant tents and concrete floors to the masses of casually dressed attendees to young speakers excitedly talking tech about instead of throwing up PowerPoint slides. There was even a couple of puppies on stage.\n[ Related: Busting millennials-in-the-workplace myths ]\nAll of this appeals to millennials, the target demographic of the moment despite the fact that many are drowning in student loans. Nearly every digital marketing trend, even in business-to-business, seems to be aimed at them. But marketing to millennials takes a special kind of approach.\n"They're an amazing group to market to, because they will not accept mediocre marketing," says panelist Dee Anna McPherson, vice president of marketing at Hootsuite. "They have very, very high standards. They're socially conscious. They want to engage with brands that reflect their values. They like to co-create with you. They really keep you on your toes."\nDon't sell to them, engage with them\nMillennials don't want to be sold to as much as engaged with. For marketers, this means the content they produce on social networks and native advertising should take a conversational tone, tell compelling stories, entertain and educate rather than push a marketing message.\nSure, millennials have been labeled as selfish and entitled, but the opposite is true, say panelists.\n[ Related: What kind of CIOs will millennials make? ]\n"There is a degree of self-centeredness, I think, with the whole sort of social media and selfie era, but they're probably the most socially conscious group out there," says panelist Kyla Brennan, founder and CEO at HelloSociety, a social media marketing and technology solutions company. "They really care about what brands are doing. They respond to brands that do good and are transparent."\n"You can't bullsh-t them," says panelist Brad Haugen, CMO at SB Projects, adding, "They're really changing the conversation."\nMillennials know when a brand is trying to play them for fools. One of the recurring themes of the panel is that millennials can sniff out inauthenticity a mile away. For instance, many marketers make the mistake of trying to woo millennials by co-opting their slang words, such as "on fleek" and "twerking." These misguided efforts can backfire, as millennials start conversations on social media that make brands look foolish.\n[ Related: How to help millennials shine in the workplace ]\n"That's the f-cking worst," Brennan says. "Just don't do it."\nOther brands are making the right moves.\nMcPherson, for instance, likes online eyeglass retailer Warby Parker, which is running a "buy one, give one" marketing campaign. The company doesn't scream its coolness message in consumers ears, rather the company lets consumers decide for themselves. Consumers can also receive five "try on" frames delivered to their homes, post pictures of themselves and get input from friends on which ones look best on them.\n"They're killing it right now," McPherson says.\nHaugen pointed to an older brand, Taco Bell, as doing a good job marketing to millennials. He says the fast-food restaurant has done a great job engaging consumers on social media, generally through humor. Haugen says many of his under-25 employees love the content Taco Bell delivers on both Twitter and Instagram.\nMillennials are the flavor du jour, and they know it. They know what technology can deliver, and so they expect brands to give them a personalized, authentic customer experience. Since they're in the driver's seat, they can also demand brands be socially conscious.\nIf Taco Bell is any indicator, millennials want to laugh a little, too.