According to this article by Kent Lewis for iMedia, it's a mistake for marketers to treat Millennials as a homogeneous group and not segment them more closely as we do Boomers and Gen X.

The Big Idea:

Although most Millennials are big users of social media and have high expectations of companies trying to sell them stuff, there some other important attributes that set them apart from other generations.

How Millennials are different:

• For them to connect with your brand, they first need to discover it for themselves.
• Reachable by educating and entertaining instead of selling
• Watch TV on various devices other than traditional televisions
• Influenced by peer (WOM, social media) and online reviews
• One-to-one marketing works if done right.
• Can be loyal to a brand if values are a good fit.
• Like to watch and share ads that are interesting and entertaining
• YuMe has identified 5 sub-segments:
  • Mobile Mavens 19%
  • Tech-Savvy Savants 19%
  • Cross-Training Cord Cutters 22%
  • Thrifty Traditionalists 22%
  • Casually Connected 18%

Successful strategies:

• Use all social media channels; mobile is essential.
• For engagement, share valuable content via social media.
• Respond quickly in all interactions.
• Tell good stories.
• To create good will, be transparent and have a good back story.
• To engender loyalty, be honest and authentic, don't be pushy.

Good article, good advice. But implementing requires a leap of faith for traditional marketers.