Saying "No Thanks"
I have found that having an excuse to say no thank you really helps. In my case I use driving as the excuse. Rather than saying no thank you I drink too much as it is I'm going to abstain tonight, i say thanks but I'm driving, a soda perhaps?
my dad said to me at Easter.. 'what? you won't even have one? that wont affect your driving'. I was luckily able to fall back on the fact that I'm only a G2 licensed driver so it's actually against the law for me to have any BAC over 0. I was surprised to see just where the pressures are coming from, I would have thought from my friends and peers, but i never suspected my older role models would have a negative affect on my drinking.
I work in a bar on weekends (bartender some nights security other nights) and often feel pressure from my boss to have a few beers after we close up, or nearing the end of my shift, I always tell him I'm driving and simply can't do it. I often offer to drive him home if he would like to have a few, that allows me to have the social drinking/bar feeling without actually drinking.
My suggestion to help people say no thank you, volunteer to be the DD every chance you get. Your friends, the community, the police and even the bar staff will thank you, and you'll have a feeling of purpose, pride, and self respect. Most establishments will offer non alcoholic beverages to a DD if they are interested in having something to drink, plus you get to still hang out with all your friends. Often if you tell the bartender you are the DD, and you 'slip' later on and try to order a drink, the bartender can help you get back on track with a gentle reminder that you are responsible for driving.