How I learnt the word crack...once upon a time in SF along Golden Gate (the street, not the bridge)...
Black : Yo, handsome Chinaboy! You want some crack?
Ram : Huh? I don't know crack and I don't do crack. (Trying to sound as much American English as possible.)
Black : It's good stuff, man. For 50 bucks (US$ of course) I can get you a good pack.
Ram : Thanks but no thanks, man. I'm hurrying for an appointment to meet a police inspector on Market and 7th.
Black : Alright man, cool man. By the way, don't tell him you've met me.
Ram : Sure man, I don't do crack but I won't sell a friend out too, shake on it?
(Shake hands
)