Same, teen peer pressure is what got me started. What really got me though was trying it and doing that "newbie" cough/hack crap. I mean everyone else who smoked wasn't hacking. But when then shit is first introduced to your system your body has that natural reaction.
Natch, instead of listening to my body, I said to myself, hah, I'm not going to let this little piece of rolled up paper make me cough like that. And as soon as I master that, I can quit at any time!
Oh yeah. Right.