At the age of about 13 or 14, my best mate and I used to volunteer at weekends at a local archaeological dig. In the summer, the director of the dig used to bring in a few cans of cider, for the workers to consume at lunchtime, and I guess that was my first introduction to alcohol.
My first bad experience with it was at the age of about 15, when I went to an open air all-day folk concert on a hot day, armed with only a very large bottle of cheap wine. The hotter I got the more I drank. The more I drank, the thirstier I got, so the more I drank..... It didn't end well......