I would make it all sarcastic. For example, "There's nothing a girl likes better then kissing an ashtray". Or, " Oxygen tanks can make a really big fashion statement". In other words, think about all the negative aspects of smoking and just turn it around in a funny matter. The reality is, it's not at all funny when you have this addiction. The only difference between a drug addict and a smoker is that smoking is regulated, legal, and sociably accepted.
I started smoking when I was 16 and quit 1yr 1/2 ago when I became pregnant.