I think the first thing to help is realizing that no amount of research is going to fix the problem. Asking for advice, like you're doing is the best thing. Even though I've never experienced alcoholism with anyone before, my best friend was really in to cutting when we were freshmen. I wanted to help her so desperatly, and after a huge fight in the library I figured out how I could help: by leaving it up to her. After a while she figured out that what she was doing was hurting everyone, and she got help.
Obviously, alcoholism is completely different than cutting, but one way is to tell that person how much they are hurting not only themselves, but everyone around them, and then leave the decision up to them. Let them know that you will always be there for support, but only when they decide to take it. The only way they're going to quite drinking is if they make the decision themselves, nothing you or anyone else does can really fix that.