Telling the bartender you like "all beer"... especially if you don't
"The number one for me is the person who comes in looking for a beer, and when I ask them the question, 'Which styles do you typically prefer? Or what brands of beer do you normally drink?' so I can guide them the right way, their answer is, 'I like all beers.' And it turns out they don't like all beers.
"If someone is coming in under the assumption that, 'Well, I like Coors Light, Bud Light, and Miller Lite, so I like all different beers.' But really, that's one specific style of beer, and trying to get them to that point sometimes is a struggle when they're not willing to give you more information about their tastes. I've had people come in saying they like IPAs, and then it turns out they hate beers that are bitter. Same thing with people who say they enjoy sweeter beers, but when I give them something with a malty backbone and a sweetness to it, they say, 'I don't know how people drink this!' Some people say they like all beers, but it turns out they only like stouts [as an example].