I smoke because it makes me look cool. Just joking...
Ok ok seriously... I started smoking becuase when I got drunk woth some of my friends, they would smoke, and offer me a cigarette. Sadly, I'm incapable of saying no when I'm drunk. I gradually started smoking regularly, until I had an "incident" where I drunkenly (very drunkenly) smoked a few Marlboro Reds the wrong way. I stopped smoking every day, but every few weeks or so, I get a craving for a cigarette. Just one, but they don't sell single cigarettes. And when I'm drinking I smoke like a chimmney, so I try and not make a habit of it.
Like Marsprobe said above me, "Ruin your own health if you want mister, just don't drag us into it as well." Quite right. Even as a light smoker (thats how I define myself), it was horrible going into a restaurant to eat and the place stinking of smoke.