"My point being, by saying "Because I am a Christian I no longer drink." it sounds like abstaining from alcohol is a tenent of the faith, or a requirement for salvation. Are you saying that anyone who drinks cannot be a Christian? I doubt that, but that is what non-Christians (with a few drinks in them!) may think you are saying.
Further, is that really the first aspect of your faith you want to talk with your non-Christian friends about? "Oh, yeah. He's a Christian now. They don't drink." Not the slogan you were going for..."
I see your point, and fully agree. And I am most certainly not saying that anyone who drinks cannot be a christian, I personally have no problem with someone having a beer/wine/whatever or two. But I feel I need to add a bit of clarification... At parties and such for my age group where there is alcohol, no one is drinking just to enjoy an alcoholic beverage. They are drinking with the singular purpose of getting drunk.
"Christians are not all in agreement over the consumption of alcohol. Scripture is very clear about drunkeness - it is a sin."
Very true, but this is part of where my hesitation lies. A few of my friends have accepted Jesus Christ as their personal savior. However, in many cases, they have made no attempt to turn from the sinful things of their past lives, e.g. getting drunk. I know that they rarely (if ever) read the bible. So I am not sure if they honestly just don't know about the bible's stance on drunkeness, or if they don't care. If it is the case of them not knowing, don't I owe it to them to answer "because I am a Christian?" Afer all, this might be offensive at first, but also it may leave them wanting to discuss my response.
"If these are the same people you see with some frequency, I would suggest saying "I'm not drinking tonight." It is true. You are not deceiving them or misleading them. If, after some time of this your new pattern is noticed, someone will probably say "Hey, you haven't been drinking at all lately. What's up?" Then you can answer something along the lines of "I've made a number of changes in my life lately..." and talk about Jesus Christ, not about booze."
This is sound advice, which I think would be an excellent way to approach this issue with non-believers. But what should my approach be with my Christian friends who get drunk constantly?