hi ian,
the best thing is of course to be prepared, hence your question. if it's a special occasion, you may decide to allow yourself 2 drinks, for example.
if it's a weekly thing with the guys after work, you can approach it in a couple of ways.
1) drink beer such as blonde. let's face it, most guys are now more health conscious than the good old aussie bloke of old... this will work well if you're a beer drinker.
2) shots of say southern comfort or whiskey, mixed with coke zero, have around 70 calories per shot. possibly not worth the empty calories (though this IS the southern queen talking here LOL)...
3) if you are going for the above option, you can then after the first drink, have nothing but coke zero. no one is going to know that there's no alcohol in it, except you & the barman.
4) water looks the same as vodka
5) if there are some other big guys among your group, i'm sure they won't argue if you just say "i'm watching my figure" (preferably followed by big blokey laugh)...
6) as a general rule, i don't drink & drive, so if you drive to work, you could use that, if you need to comment on it at all...
7) last but not least... don't worry about what everyone else thinks!!! it might be a case of getting a thicker skin, or coming up with a witty comment, but at the end of the day you do not need to explain yourself to ANYONE! (unless you break the law, then let your lawyer do the talkin'!)...
You may feel, if you're just starting to get your health & weight under control, that everyone is watching you with a magnifying glass (which i kind of think is the feeling behind the pork pie at a barmitzvah comment)... the fact is, unless you make it obvious for everyone, the best thing to do is keep your lid on, because most people just aren't that observant... besides they're most likely worrying about their own personal internal dialogues ("the wife'll be p*ssed if i drink too much", "the boss is working me too hard", "how am i going to get X done on the weekend with all this other stuff"....) I'm sure you get what i'm saying here...
In the end, go with whatever makes you feel comfortable. In the end, it's better to choose not to drink (from a weight-loss point of view) but if you feel you need to, then only have one & fake the rest....
Kaz x