I find one effect of alcohol is to lower my blood sugar, so as others have said be prepared to test a lot the next day and if necessary adjust your insulin.
But the main effect of alcohol is to make me careless of what I eat: when I was on insulin (fixed dosage) this meant I tended to guess the carb content instead of working it out; now that I am diet controlled it means I'm more likely to give in to the temptation to eat pizza, crisps etc. I try to counteract this by lining my stomach in advance by eating something fatty and filling; in my case I just drink double cream, but if you don't like that or are no low-carbing then milk and porridge work well.
It's also very useful to have a buddy: someone who knows about your diabetes, knows how to spot a hypo and is strong enough to intervene even when everyone else thinks you're drunk and keeps encouraging you to drink more or laughing at you because they mistake a hypo for tipsiness.
Also, remember it's perfectly OK not to get paralytic: you can do the usual things such as drinking slowly, interspersing alcoholic drinks with water and drinking tonic or fizzy water with a slice and pretending it's a gin and tonic.
Kate