Don't smoke. Never even tried, not even when drunk. Morally superior ain't I? *Titter*
My brother does. He was 14 when he started - now he's 15 - and it's definitely because of his friends, who are all probably going to jail (not because they smoke, for other things, smoking is just one of the things they do).
Now if you want to know why I started drinking, it was initially to alleviate some girlfriend blues (I'd been dumped recently). It works at a certain level of drunkness, just not when you slide too far over the threshold, if you get my meaning, otherwise you can become a wreck in a few seconds (and that ain't good when the girl in question is in the room - that was an amusing night in hindsight). Then I liked the feeling of being drunk, and began to get accustomed to the taste. I'm a social drinker now (usually spend about 3 or 4 months without a drop, since it doesn't particularly bother me), and I think I'll stick to that. I'm unlikely to regress to a state of nothing, or progress to all sorts of narcotics (interesting usage of regress/progress there).