Imagine you are standing behind the bar with your co-worker and swarms of rowdy customers surround you. Where do you start? Can you make out any of the words? Usually, when someone wants a drink they will make themselves known, so you have to start somewhere. You could take one end of the bar while your coworker takes the other side. Or you could just pay attention and work your way through the crowd at random. As long as you don't get overwhelmed, and are sure to maintain your groove with confidence, you will be just fine.
"I give priority to the customers who have their money out and are making eye contact with me. Someone may be there first who is on their phone and not paying attention. I don't interrupt them from their phone because I assume they aren't ready to place their drink order."
Entry Level answer example
"I have not experienced working in such a busy environment, but I am excited about the opportunity! If I had many customers waiting for a drink, I would treat it by first customer ready to order. Some customers may be ready to order, and others may just be standing at the bar, chatting. You have to be able to differentiate between the two customer types."
Experienced answer example
"I serve the customers that make eye contact with me, indicating that they are ready to put in their drink order!"