Alcoholics...

Well, I don't think it needs to be too obvious. Not all dysfunctional alcoholics leave empty bottles around or stumble in shouting at 4 a.m and black out on the kitchen floor...and those types (in writing) tend to feel one-dimensional and stale.
Most alcoholics have a reason for being that way, other than just liking booze. What's the dad's catalyst? Was it gradual or sudden (the development of his alcoholism)? If you lay some background, it may be a little easier to figure out what his drunk behavior will be like, since it's usually a worse or more exaggerated version of the person's usual self. But with alcoholics, there's no usual anymore.

Maybe he used to be incredibly charming when he was younger (and knew it), but now it's like he's pushing himself on people...thinking that he's being his old self (cause the alcohol convinces him of it) but he's obnoxious and arrogant now instead. Wakes up ... and cringes to himself... ? the cycle of remedying the symptom with the cause.

You could have him get mad at people who aren't there when he's drunk, and start having discussions out loud with them in front of his son (people from his past, people who give him advice that he doesn't agree with).

He could be a cryer. One of those people who is in pain because of X reason, and every day thinks that drinking will help, but after the first few drinks (which make him feel better) he disintegrates into a weepy sap. Maybe he tries to get comfort from his son, but only tries when he's toasted, and the son thinks it's repulsive and shuts him down...

I don't know--these are actually some people I am around (none of them are like this all the time...and most of them have more than just one drunk shtick). I think most alcoholics (of course) don't think they have a problem. Most don't; the only problem is that their liver is about to pass out. So it's usually about something other than the amount they're drinking...it usually has to do with why.

Hope this helps! Good luck

If you want to make him seem distant, I think making him forgetful would be a good way to do it. He has conversations with the MC, and some of them seem meaningful, but he never remembers in the morning. He's completely unreliable and makes her promises when drunk that he later forgets. He promised her he'd come to [insert important event here], and then never showed up. He could sleep A LOT, at weird hours. This would all indicate something was wrong without explicitly showing him drinking. But if you want to show him drinking, make it seem super routine and maybe show him drinking at odd times during the day (morning). If he's open about his drinking with his daughter (which doesn't mean he thinks it's a problem--he could be justifying it) he might say "let me pour myself a drink first," whenever she asks him to talk to her or do something with her. I don't think there is one set patten of behavior with alcoholics, but these are all things I've observed first-hand.

As for getting help...if he misses a big important event in her life (something like graduation), this could wake up him to realizing he has a problem. If you don't need the decision to come from him, getting a DUI would pretty much require him to get help.

As for how it would affect your character...well, it really depends on your character. She might become more independent because she knows she can't depend on her dad. She might start drinking too, because it seems easy and it's already normalizd for her. She might make excuses for her dad and take care of him, or she might resent him and be counting the days until she'll be 18 and she can move out. I think you could go a lot of places with this and have it work :)

The first thing the father can do upon waking is go to the fridge for a drink. Even if he's woken in the middle of the night to go to the toilet. I agree with the comments on forgetting events. Eg, might have to pick kid up and not turn up and they've got to find their own way home. An alcoholic doesn't necessarily have a reason why they become an alcoholic. Some people just don't know when to stop. Nor do they see what they are doing. Things like forgetting to pay bills like phone and electricity are common, maybe the MC would have taken over the running of the household by this stage. A mature child can efficiently run a household at 10 years old, including prepare elaborate meals. There could be some arguments over events that the father doesn't recall happening as alcoholics have poor memories, especially if they have been drinking for a lot of years. You could mention the rattle of bottles in the bin when the MC puts it out on garbage collection day. If they do the housework, maybe a bottle on the bedside drawers regularly has to be thrown out. Not all alcoholics hide their drinking as they think they aren't drinking excessively. The MC would also have learned the best time to ask the father for anything, eg money, to go out, etc, would be when he's had a few drinks. The father is also likely to have a 'beer gut' and if the drinking has been going on for a long time, he could even get the shakes if he goes too long without a drink at any time. Eg maybe held up in traffic on the way home from work. Not all people act noticeably drunk when they've had too much to drink. Some people become quiet rather than abusive or talkative when they are drunk. And an alcoholic doesn't have to get completely drunk every day to be considered an alcoholic or for it to effect their memory and behavior. You're welcome to send me a message if you want to run a particular scenario past me.

You are what you consume- whether it be words on a page or food on a plate.

Thank you to all of you for your insightful suggestions.... you've given me lots to think about. Good luck on your writing & thank you so much again!

Hey, don't know if you're still looking for info... but my father is an alcoholic so i guess i can probably offer some realistic views. In his case, i don't really know what started it, he's always drunk a lot, but i guess he started drinking more after his mother died, to a point where i am now surprised if he doesn't drink. He still won't admit he has a problem. He's difficult to talk to when he's drunk because he can't quite follow a conversation, always asking what and making you explain things a dozen times, or talking about something completely different to what i'm talking about. Of course in some ways this is preferable, as he is at least nice when he's drunk, when he's sober he tends to be angry... don't know if this is any help to you... but thought i would write anyway... if you want to know something specific pm me.

Another random thing about alcoholics:

Because they have an addiction to alcohol, the chances that they will be addicted to another substance, be it dangerous or not, are much higher. One of my family members is an alcohol, and she's also addicted to cigarettes, so she's smoking constantly. And there's no coincidence between the two. Coffee is another big one.

Thanks for the new comments... this is so helpful.