First, you get really, startlingly, tired. You should find some alternate food source, and even, I dare say, cut out caffeine at the same time you cut out alcohol. Not that I'm a model of this behavior at the moment. And you'll get very grouchy.
Second, you'll probably feel like shit about yourself and the world around you. Over time, this feeling will dissipate to be replaced by the notion that, blandly, the world doesn't really care about your drinking habits. Whereas before "everything" mattered when you were drinking, and everyone cared, and drama abounded, not drinking can be boring at first, because we drinkers were so oriented toward drinking when there's nothing else to do, or drinking when there's everything else to do, etc.
Third, you'll stop hanging out with at least three-quarters of your friends, and realize that you'll need to find alternative models of behavior if you want to continue not drinking. As comfortable as you might say you are to friends who drink and go to bars (when you're invited), let's be honest and say it like this: going to bars isn't that much fun, and can bring out small (or large) anxiety attacks that persist long after the environment changes.
Fourth, you'll want to do something with your heretofore worthless life.
Fifth, you'll realize that doing something, whatever it is, is really, terribly, difficult. And yet. Having freedom from pressure can be very easy in moments of transition.
Sixth, you'll be forced to face some of your own hard seeded emotional irrationalities and either affirm or confront yourself before moving to fast-sinking plateau of utter insecurity about what you've previously believed about the world. This is actually a good step.
Seventh, you'll write a blog post about this, and hope that you're convincing about the last part. At least to the one person who matters....