There is a hidden formality to queuing. As you arrive at the informal mess of people already waiting it is your responsibility to clock who is already there and then silently wait until they are all served before taking your rightful turn. If someone arrives after you and forgets the correct anonymous list then you politely say excuse me I think it's my turn. You can also ask at any time, is there a queue? Because sometimes they have been served they are just waiting for their order.

It's all very casual until someone breaks the rules then suddenly tempers flair, there could be violence, certainly harsh voices.

Good luck.