Quantity over quality
People are impressed by big numbers. How much money do you make? How much did your car cost? How many women have you slept with? The list goes on.
How about... how much alcohol do you drink?
Typically, however much a person says they drink, you double it. People minimize their drinking, often unconsciously. When I first started asking this question, when we were seeing agreeable and carefully selected patients, I often got answers like "a glass of wine with dinner" or maybe "a couple beers a night". If you double that, it's certainly more than you ought to drink, but it's probably not going to kill you.
What about a case of beer? Am I supposed to double that? When would you find time to drink *two* cases of beer in one day? I do think I'm slowly starting to figure out who is honest about their habits... like the guy who tells me plainly that he typically drinks a liter of vodka a day, but didn't have that much yesterday, because he woke up in the hospital before he had finished his liter.
Seriously. And I shouldn't say "that guy" because a liter of vodka seems to be a popular answer. That's the good amount of vodka. And how much do you smoke? Five packs a day. Want to hear another good one? How about heroin? 30 bags. At least that guy only drank a pint of vodka with his 30 bags of heroin.
I don't know why I continue to be surprised by this stuff, aside from the fact that those quantities would kill a normal person. Or the fact that many of these folks are dirt poor, and yet somehow financing these extravagant habits. The best part is that often these people are in the hospital because they're not taking their medication. Why? They can't afford it.

I don't really have a comment, just wanted to say something along the lines of
"Whew."
or
"If we were in a jazz poetry club, I'd snap."