In reply to outtathaway:
lots in the above that is along the lines I would have said explaining that different drinks effect people in different ways. Vodka is usually a good one to try first if you're narrowing it down.
Time off and fitness could help.
If you're going to stop, some advice, learned from time off the booze and recent cutting down a lot -
1/ alcohol free beer ain't bad. (ok a few are) and are getting more commonly offered too. Ok it'snot as good as the real thing but if like me you don't want to be drinking gallons of coke it's well worth trying. (and it's normally quite a bit cheaper than the alcoholic ones)
2/ drive everywhere! It will prevent some of the peer pressure and set you a hard limit of "I CAN;T be weak because I'm driving.
3/ don't be apologetic or embarrassed about not drinking! lots of people are and that's a bit reason people push you to drink, because they can see you want to and they want you to have a good time. Stand by your decision and if necessary explain exactly why you're not drinking and they'll step down. If htey're still being tw*ts about it then decide if you can stand it or whether you should be avoiding them.