It's no secret that marketing to teenage girls has always been challenging. The good news is that reaching this audience is not an impossible task. In fact, here are 10 emerging best practices to consider when preparing to connect with teenagers: 1. Most brands are totally irrelevant When it comes to things like fashion, teen girls want to associate themselves with a limited number of brands and have little time for anyone else. As a brand, if you're not helping to create a girl's personal image, what are you doing for her? 2. Plan to lose them and have a strategy to bring them back The fact is that teens try on brands like they do identities and rarely, if ever, will you secure their loyalty. Brands should be prepared to lose them -- probably more than once -- and then have a strategy in place to bring them back. 3. Enable multiple personalities Choice leads to fragmentation and teenage girls love to try new things. Marketers should look to help facilitate this rapid form of marketing prototyping by offering free samples and online demonstrations to help them envision how the product fits into their lives. 4. Provide (offer?) places to talk and ways to share Social networking sites are the glue that hold teens together. Compared with the total mobile Internet population, teens are the biggest consumers of social media, music, games, videos/movies and technology/science. By giving teens opportunities to share, discover, mix and communicate, brands can influence them, get them to take action and light up their own network. 5. Create a cause Parents are no longer the targets of teen rebellion. In fact, they have been replaced by ideas, organizations and brands that teens perceive as harmful. Today's teen wants to make a difference and is susceptible to cause marketing because of their generation's intrinsic altruistic sensibilities. For brands, the key is to incorporate charitable campaigns within the context of their day-to-day lives. 6. Don't undervalue TV programming While many view TV as diametrically opposed to social media, the truth is that it can serve as the perfect complement and should be used to support online experiences and build brand platforms. TV viewing is on the rise among children and teens, and the biggest media gainer is video viewing on the Internet. Teens also use their mobile phones to watch videos. The key is to figure out how to interact and engage with viewers before, during, after and beyond the program. 7. Let teens be your marketing department: In asking teens why they started to use specific genres of social media, Harvard Berkman Center Researcher Danah Boyd heard a common refrain: "That's where my friends are." Teens adopt the tools that their friends use and in doing so, they influence those around them. Marketers need to find and leverage teen influencers and trend leaders and let them act as brand activists. 8. Give them the tools: If given the choice between A and B, teens will chose to create their own C. Teens are the media and content creators of the Web. Jonas Brothers and Taylor Swift are teen phenoms -- not because they are inventions, but because they write, create and do their own stuff. They are agents of their own exploration and experimentation. Brands should strive to give teens the tools they need to help them discover, express themselves and create new things. 9. Don't forget Mom: Ask a teen girl who her BFF is and 86% of American teens will say their mother, according to the TRU Study on Global Teens. Today, Moms are the teen girl's confidant, serving as curators of their teens' purchasing habit and the primary drivers of purchase intent. For instance, according to a new study on Teen Health Perceptions, parents are the leading sources for health advice. According to the study, 63% of teens say that when they have questions about health and nutrition, they go to their parents/guardians for information. One half turns to the Internet. 10. Some old rules still apply (maybe more so) Because they're still teenagers, these girls haven't learned how to fake authenticity. Instead, this group is as genuine as it gets. As a result, it is critical for brands to be transparent and trustworthy if their goal is to build brand preference. Looking forward, this column will strive to continue examining the teen audience and provide readers with additional insights that help them engage this group more effectively.