I'll have a pint of bitter before a gig sometimes just to loosen up a little, but that's about it.
I've learned that late nights+ alcohol = wasted day after.
But that's great in some respects because I can really push the boat out on some nights if I don't drink. For example, I went out last night to see Prince, came back at 5am, didn't touch alcohol the whole night, got about 5 hours interrupted sleep (it was a day off) before getting up feeling pretty sharp and I attended a very successful job interview this afternoon.
If I'd been drinking the previous night, I'd have looked like death warmed up and been more or less incoherent.