BYCU
This article had great humor potential: 19 Tips for Staying Catholic when you go to a Bar. Unfortunately, the author is serious about giving tips to young Catholic professionals who need the bar scene as part of their social network (I used to be one of those guys; it was a good time).
The piece has some good tips (e.g., don't keep looking at your phone), but I wish it spent more time talking about what constitutes "too much." For purposes of mortal sin, "too much" is drinking to the point where you lose the ability to reason. I once said to a priest (actually, three priests) that you'd have to be awfully drunk to reach that point, and they said, "Yup. It's not easy to sin mortally through drink alone." Of course, the things you do while drunk can land you in mortal sin and drunkenness is generally no excuse, so you need to tread carefully, but I've frequently taken comfort in that high hurdle for mortal sin, especially when I've been in the throes of a hangover and the dreaded "metaphysical hangover" (Kingley Amis' term for that general depression a person feels upon waking up from "too much").
But when does drinking lapse into just a venial sin? I mean, a drink or two is no sin at all. It, in the words of the Bible, gladdens the heart, which, no doubt, is a level of inebriation, if only slight. Twenty drinks is mortal. But surely that vast land of fun between 2 and 20 isn't all venial, is it? I conducted a brief Google search, but it produced nothing useful.
So, after much cogitation, I produce herein the TDE Source of Doctrine for When Drinking Lapses into Venial Sin: When you drink to the point that other temptations that are normally kept at bay become a near occasion of sin.
So put that in your shot glass and drink it. Or reject it. I am, after all, just another Catholic with a drinking enjoyment who's waiting to get the nod from the College of Cardinals.