I'm 19 and been smoking for about 6 months now.
Several reasons for starting, all as stupid as the rest:
1) I started working in a shop that sold smokes. Since I believe in "Don't knock it 'till you've tried it" I thought I'd see what the rage was about.
2) I had a very, very bad split-up with a (now ex-) long-term girlfriend. She, and me too at the time, never saw the point in (using the exact phrase) "putting a stick in your mouth and setting fire to it". I became an alcoholic and violent, and naturally smoked because she used to hate it (this is all once we separated).
3) It curbed my violence a little. I found that when I stormed off (to stop me smashing in the faces of my friends who, honestly, had done absolutely nothing to deserve my rage, I was an alcoholic with issues) being able to sit on a motorway bridge and have a smoke calmed me right down (not in the sense of jumping off a bridge, I just find watcihng the cars go by on a dark night is really relaxing [this bridge is in the middle of nowhere, it's pitch black, so the lights from the cars are quite theraputic]), and stopped me doing anything stupid that I knew I would later regret.
I basically smoked whenever I was out drinking (once or twice a week). I still do, as it is something quite nice to sit around outside on a nice evening having a smoke and a chat with some close friends. Also, in many clubs these days, you can't go into the outdoors smoking area *unless* you are smoking, so it's an wxcuse to get outside to cool down a little.
However, I've recently started smoking on the way back from work, to the tune of 1-3 a night (sometimes Superkings). This is really affecting my running performance, so I'm trying to stop this altogether. I took part in some clinical trials at university (I needed the money) and they found that although I am receptive to high-doses of nicotine, I do not suffer from any typical signs of addiction.
Speaking of the nicotine - the high you *can* get off a cigarette (or for me half a pack) is something to try once, if you are so inclined. Your heart races, your senses are sharpened and you feel like you could kick the world in the bollocks and get away laughing (or maybe that's just the eventual effect on me, I dunno). That's why I some after a bad day at work, socially I only smoke one or two, so don't get any sort of buzz at all.
Now, me stopping smoking on the way back from work is harder than it sounds, even though I am not addicted - I have about 12 packs of various types of ciggies, and I feel like I would be wasting my money to just throw them away - so the "smart" thing to do would be to smoke them all as soon as possible...
...once I have dealt with that stupidity, I can get back to only smoking one or two ciggies every week/fortnight when out at the pub with friends.
Oh wow, wordy. I really should learn to be concise!