I'm gonna bump this topic as it's an extremely important subject to our trade.
Personally, I stick with one beer if I'm driving, before or after the gig (preferably after), but only one.
If I'm not driving, then I might take a couple more, but I don't enjoy being "shitfaced" kinda drunk, so I tend to limit myself to 3-5 beers, no more than one before, the rest after the gig.
Still, I tend to do the same thing while drinking socially, due to reasons stated above, the whole experience is so much more rewarding that way. This usually leads to me being the driver for nearly every night out, which in turn have lead to my friends thinking that I have a problem with alcohol.
Another good tip is to don't act like everybody is lesser than you because they drink and you don't, I personally can't stand these types, whether drinking or sober. I have this theory that these kinds of persons really would like to drink, but for some reason or not don't, and the only way for them to not drink is to consider everybody else less of a person. I'd say let everybody do what they want, as long as they let me do what I want to. Then again I don't like people that act like arseholes drunk either, if you can't act like a human drunk, don't drink.
I might add that I have too many alcoholics in my family to count, luckily I didn't inherit the addictive gene, but I like to stay on the light side just to be safe.
Everyone would probably benefit from seeing a real alcoholic (the 24/7 kind) or someone who has had an acid trip go really bad (that guy is luckily not in my family nor one of my fiends, still a real eye opener).