There are some positive and negative influences in young people.
Here is a positive influence example, if there is a sport that is getting a lot of attention by the media and gains popularity among your friends and society, you will more likely want to practice the sport and be cool with all your friends. The result is that you will have fun with your friends and be more healthy because of the exercise your are doing.
However a negative influence in teenagers is the use of cigars by celebrity movie stars, the constant exposure of sex images, the excessive images of violence and exposure to thousands of junk food ads.
Young people are in a stage of life where they want to be accepted by their peers, they want to be loved and be successful. The media creates the ideal image of a beautiful men and women and tells you what are the characteristics of a successful person, you can see it in movies and tv. Its a subliminal way to tell you that if you are not like them you are not cool yet so its time to buy the stuff they buy and look like they look.