The first thing you have to know is that sometimes people find it hard to understand why someone would not be drinking alcohol if it was offered. People almost take it personally or feel like they are being judged when someone suddenly stops drinking. There is definitely a stigma around sobriety and there are many negative and unfounded assumptions about non-drinkers, such as they’re lame, boring, and not fun, they’re purposely not drinking to be a stick in the mud and kill everyone's buzz or they’re snobs who think they're better than the drinkers. If you feel your friends are thinking along these lines, you may need to examine your social circles. A good friend will be happy to help you cut back on drinking
I’ve been at the receiving end of it myself. If I look tired, bored, or annoyed for so much as a second during the evening, I’d sometimes get pounced on and told I wouldn't be feeling that way if I had some drinks, or people well-meaningly, but condescendingly, try to "help" me loosen up and come out of my shell by cajoling them me drink a little.
If you feel like you cannot survive the stigma around sobriety, there are a few things you can do to avoid suspicion. If you have an event at a bar or restaurant, I would suggest arriving a bit early before the others and talking to your bartender or waitress. If you let them know you are not drinking this evening, but you don’t want anyone to know, they can make you fake drinks that appear to be alcoholic beverages, but are really just club soda or mixers without the alcohol. Many times, the glasses they use at bars and restaurants denote alcoholic beverages from non alcoholic beverages, so if you arrive ahead of your friends and they see you with a clear glass filled with ice and garnished with a lime, they will just assume its your usual gin and tonic, even if its clear soda or seltzer water. And if you can’t make it early to to location, don’t fret, just try to pull your waitress or bartender aside and discreetly let them know your preference for the evening. Bartenders especially will understand this and are usually more than willing to oblige. Just make sure you pass them a good tip at the end of the night for keeping your secret safe, after all, you are saving a good amount of money if your drinks are dressed up sodas without the shots of alcohol!
If you're the designated driver, or you truly have to get up early the next day, or you're seriously training for a sport, no one can really argue with you that much if you don't drink. The situation prevents it. Of course, sometimes you'll still get people who say things like, "You have to drive?! Yeah, like in three hours from now! Come'on, one shot won't kill you!" However, having these legitimate excuses will reduce some of the arm twisting.
When you’re at someones home or a barbecue obviously its a little harder to control this situation, but there are things you can do to avoid alcohol without people pestering you about it. First, I suggest bringing some drinks of your own. Usually, if your attending a barbecue or a party at someone’s house you would bring something like a side dish or a bottle of wine etc. Well, make sure you bring yourself something to drink without alcohol in it.
If you are normally a beer drinker, I suggest picking up a 6-pack of a micro brew root beer or ginger ale that you can find at your local supermarket. Often times these microbrew non alcoholic drinks appear to be actual beers as they are packaged like them. You don’t need to say anything about what you brought, but if someone asks you and notices its not a beer, you can say something like “I really love this stuff, its my new addiction!” People may offer you something alcoholic, and you can politely pass on it with the legitimate excuse that you brought your own. I find with situations like this, people aren’t so concerned with what you are drinking as long as you are drinking something that looks familiar.
My second suggestion would be to bring a pitcher of a beverage that looks like a mixed drink. Make a colourful drink and stick to it for the event. If someone asks for a sip, let them have it and revel with them in amazement at the fact that you just can’t taste the alcohol! “Maybe I didn’t put enough alcohol in,” you can suggest. Your not lying and your friends will probably end up avoiding your beverage for something stronger anyway. In the end, everyone wins and you most of all win for avoiding alcohol without feeling the peer pressure of your friends.