Drinking is not cool. It doesn't mean that you are mature. It just means that you cling to something that you think makes you feel better about yourself. Chances are you need something better to do with your life.
People under 30ish that drink (I generally believe that older people started drinking, smoking, and other things before the true harmful effects were known to the general public) are followers at best. They watched tv and friends, and this is the only thing they knew how to do when getting away from mommy and daddy.
In some weird parts of the world, drinking is even associated with toughness. Drinking doesn't make you tough. At best, it makes you stupid.
Given that most of the world's population are followers at heart, it is futile trying to make this point because normal individuals cannot beat society.
You have to take it upon yourself to realize that you are wasting your time and money.
As a social drinker who enjoys the taste of good beer and liquors I have to disagree, there is nothing wrong with drinking, its fun and makes for good discussions.
As for the OP, I find the best solution to police issues involving under aged drinking is to have a good story set up and lie. In the US we have an artificially high drinking age limit, what the cops don't know can't hurt them. Just make sure your friends are in on the story and you'll be fine.