You enter drinking sessions with a set of actions and the gold you got from dungeon raiding. Your objective is to leave with as much coolness as possible. There are two intermediate attributes to keep track of while trying to process your gold: attention and sobriety.
The amount of attention everyone else in the bar is giving you is the main currency of actions. At zero attention, nobody else can target you with actions, since nobody cares that you're even there (or maybe you left, who cares?), but you can't do most actions yourselves, since nobody is watching you be awesome. The most common way to get into the game and get attention is to by someone a drink. Drinks grant 4 attention to the drinker, and 2 attention to the buyer, and deals sobriety damage to the drinker (you can get 6 attention by just buying it for yourself). Drink costs are publicly displayed, but drink potencies randomized every few days, and you will have to learn the drinks of the day by trial and error.
Anyone can play actions at any time. For the most part, you pay the cost of an action the moment you play it, but the effects don't come to pass until the action goes off. Once played, the action enters the pending actions queue. It will stay there untill 20 seconds passes or the action is reacted to, at which point the reaction will enter the queue and wait for 20 seconds or until a new reaction is added to that stack. Note that there is still some lag in the system, so often the data on your screen will be a few seconds behind.
The actions avalible to you will always be 5 actions, some randomly selected from your list of actions you bought at the store, as well as at least one action to buy a drink. The mechanic biases against, but does not disallow, the same action being selected twice. The targetable players list will always be all players with positive attention. Your reactions will always include the automatic reactions, and every one of the reactions you bought has a 50% chance of appearing (to a maximum of one reaction of each type). The more of a reaction type you have, the more likely you will have that reaction. You are allowed to buy more actions at any time (the server needs to be up)
Some actions require you have some sobriety damage, but letting it get too low will render you unable to engage in certain actions. Every type of action has a difficulty. You can use an action as long as your discipline - your sobriety damage is equal to or greater than the action's difficulty. If you ever drop to zero or below, you will be unable to take any actions at all. You can only get a rough estimate of the sobriety of your rivals: they will display as "Drunk" if sobriety is in single digits, and "WASTED" if it is below 1.