According to Al-Anon, we are supposed to "Detach With Love." This concept in itself is difficult, because we're so used to running around covering for our A's.
I tried mine in two steps. For the first step, I tried to detach from getting wrapped up in the alcohol. It worked, at least mostly. He didn't hide his drinking from me the same way he hid it from his mother. He was always open with me about when he was drinking. If I asked how much he would frequently give me too small a number, but in a way that could be attributed to the fact that drunk people aren't good at math, plus he never wanted to admit to himself how much he drank - so I always got the number that he was trying to convince himself he drank, rather than the number he'd tell a stranger. He also stopped trying to hide the empty bottles.
I also made it clear to him that he couldn't blame me for his drinking, because he was the one who decided to do the drinking. I said I could help him keep track of how much he had if he wanted me to do so, I could remind him he didn't want to drink, but I couldn't keep him from drinking. He accepted that, although he did sometimes try and claim that I could do a better job because I didn't do enough to remind him not to drink. Still, it was a major improvement over before, when he always blamed me. Also sometimes he would give me a bottle that he wanted to have around "just in case" to hold onto and hide, so he couldn't just go and get it when he felt like it - with the understanding that if he asked for it, I'd remind him he didn't want to drink anymore, but if he kept pushing I would give the bottle to him (which I did).
At this point, I had a pretty good idea of just how bad the problem was, just how much of his life had become centered around drinking, and just how quickly he was going downhill. If I had stayed on this level of "detachment" - not driving myself crazy about how much he was drinking - my life still would have been consumed with alcohol (in this case, "helping him" stop drinking, which doesn't work, I know for a fact), but it was an important step for me because now I had an objective view to the alcohol consumption, plus a little experience with "detaching" from a specific thing - just had to make it global.
This is a "safe step," because it makes things easier for you, but also easier for the A - XABF didn't have to hide anything anymore, and at this point, he liked that. In my XABF's case it did not make him drink more, because I had a pretty good idea of how much he was drinking before as well, and the pattern stayed the same, as did the gradual escalation I had noticed prior.
The second part of my detachment was to remove my emotions from his. I could empathize with him, but I couldn't allow myself to get wrapped up in his upsets, which was a significant change because everything made him upset. I would empathize, I would tell him I was sorry he felt the way he did, I would apologize only if I had genuinely done something wrong (and I wouldn't continuously or desperately apologize, although I would apologize more than once if he was being civil but needy).
This step started to help me, until he realized what I was doing. In my case, my XABF was also abusive, so when he didn't get the groveling self-depreciating response he wanted, he started escalating at a terrible rate, and doing things I'd never seen him do - all in the timeframe of about three hours. He didn't get too physical with me (he was very "in my face" but only grabbed me a few times and let go almost immediately), but the rate he was going I decided to remove myself from the situation.
So that part didn't go as planned, although I have heard stories in my Al-Anon of people with non-abusive A's where it worked.
So "detach with love" is the best way to go, just keep your eyes open.
If your A is going to be abusive, it's going to escalate while you're trying to detach, so I'd review the warning signs so you're prepared - just in case.
(Most A's won't become abusive - but better safe than sorry. Also, abusive usually starts as verbal and/or emotional first, which can actually cause more damage mentally, but can also give you a giant warning before it becomes life threatening.)