Straightedge= don't drink, don't smoke, don't do drugs. Other people who claim 'edge go beyond those precepts to include not engaging in promiscuous sex, adopting a vegetarian or vegan diet, or not consuming caffeine or prescription drugs.
For me, I just do the don't drink, don't smoke, don't do drugs, and don't engage in promiscuous sex. I don't like to drink soda, but I'll bite the bullet if that's the only non-alcoholic offering. Soda still tastes absolutely nasty to me. I gotta have my afternoon cup of good coffee, though. And I'm not vegetarian.
My friends in the local punk scene are really supportive since many of us are vegetarian, vegan, edge, or whatever. What surprised me was that while all my peers think it's great that I'm 'edge, it was my cousins at a mini family reunion a few weeks ago who repeatedly kept pressuring me to have a beer with them, not quite "getting" that I take 'edge seriously. Like Nuri said, it gets hard sometimes when the center of any social scene is a bar or some sort of event involving drinking. I don't enjoy going out to bars any more, because I don't drink. It gets hard when "normal" people think you're strange because you don't drink. Of course, anyone who's a vegetarian probably gets it worse because meat is key to the diets of most world cultures.
I used to drink a fair bit. I LOVED beer and was into beer tasting (I loved ales, porters, and stouts.) I still have notes on some of the beers I've had. I tried going a month without drinking last August just to see how I felt (at the time I was limiting myself to 1 beer a week), but after that month I had massive beer cravings. Then back in late December last year or early January this year, I cracked a bottle of Dogfish Head (one of my personal favorite beers) and it tasted like poison to me. That's when I knew it was the right time for me to go 'edge. It's not an easy commitment, but I don't miss booze one bit. I also learned recently that alcoholism runs in my dad's side of the family so I dodged that bullet big time.