Be forewarned I am not a expert at all on this topic and haven't had a drink myself so I am by no means an expert but I am observant when I want to be and that has allowed me to pick up on a few things so here goes, 10 signs someone is getting drunk.
1. Their eyes become slightly watery
This is probably the most subtle change on this list but if you look close enough their eyes are slightly more watery than someone who is sober, not to the point of looking like they will cry but it's there.
2. EVERYTHING is personal
Okay this might just be with some people because there are different types of drunks and all but they take everything personally and pout. For example, my dad was borderline drunk and got into a heated discussion with me and my mum and anything we said was "obviously" meant to personally hurt him etc., not just him being lazy.
3. They get on well with other drunks
You will likely notice the drunker someone is the more they drift towards other drunk people. I guess it's like drunk people can't understand sober people and vise versa, I guess they find it easier to understand them and therefore drift towards them and will talk more with them.
4. They are sentimental
Say for example you have two old friends together who don't see each other often and they both get a bit drunk they will likely drift towards each other and just talk to them for hours and regardless of how boring the conversation gets to be fully engaged. I can't really explain this but I tried hopefully you get what I mean.
5. They often lose the concept of personal space
Yeah pretty self explanatory.
6. They ether lose 90% access to most of their brain or don't take themselves seriously at all
This basically just gets worse the drunker someone gets and I shouldn't have to explain this to you.
7. They begin to slur their words a little
This is often very slight if at all happening but they will begin to miss pronounce words and slur a little.
8. They eat slower
Yes I somehow noticed this leave me alone, but generally when someone gets drunk (this might just be some) they eat a lot slower than usual and you know that sound that your dad makes when he finds a piece of food he likes? That moan thing? Yeah, that happens A LOT.
9. They are less coordinated
This is often associated with people who are already drunk but is also with people who are not fully drunk, for example I don't think someone would be able to do a puzzle as fast on 5 shots of vodka as they would sober, it's also the reason you should never drive drunk.
10. You can smell alcohol on them.
Yeah everyone already knows this but thought I should mention it anyway.
So that was my 10 signs someone is getting drunk hopefully this helps you in some way or another.