I think the concept of "teaching someone how to drink" is quite foreign here. Most people figure it out themselves - you get wasted a couple of times and you take it down a notch. That's how it was with me. I think I stared at 16, which is rather late here - the first time I saw a classmate drunk we were in 7th grade, and that was 11 years ago. By the time I was 18 I had figured out that alcohol-induced memory wipes aren't nice, so I stopped drinking too much. At my graduation ball I drank very little - a bottle of wine, shared with my date. But there were also a couple of guys who got drunk quite fast and now probably don't remember a minute from that night. Thing is, prom is seen as the day you go all-out - you're the loudest, shiniest, prettiest, happiest person at the noisiest party. It's less about celebrating your graduation and more abour celebrating because it's time to celebrate. Combine that with the common idea of "I'm drinking because everyone else is" and a sort of perverted Bulgariand Dream of rakia, chalga and ass and you get Bulgarian prom.
So the ones who are your influence on how to drink are those, that have a wrong idea about it - "Get drunk, it's what all the cool kids are doing". But there's hope - people are getting used to the idea that kids are drinking one way or another, so instead of stopping them, they are teaching them about it. For example, my dad gives my sister, who is 16, a glass of wine at dinner or at celebrations. He himself sets an example by drinking very little. It's better that she gets used to this manner of drinking, rather than gulping down vodka with kids who don't know what they're doing.
Also, I too have helped a friend of mine to see that drinking isn't just something you do, and then you get drunk. Drinking is about having fun and when you have too much, you've failed.