They're the people who can determine whether you have a night to remember or a night to forget. And as tastes in drinks grow more sophisticated, the skills demanded of the person on the other side of the bar have developed well beyond the ability to pull a good beer.
But what does your bartender really think about you? And what's the best way to impress them to ensure that you have the best possible night out?
To answer these questions, news.com.au turned to Liana Oster, an award-winning Australian mixologist who took her love of the perfect cocktail all the way to the United States.
Oster learnt her craft at some of Melbourne's hippest bars — including the exclusive Bar Americano — where her drink-making prowess and sunny personality scored her 2017's Time Out Bar Awards Hot Talent prize.
The magazine describes her as a someone who'll "stir down the classics, get your backstory, provide dinner recommendations and even help you find your way to the airport if that's what you need".
After making her mark in Melbourne, Oster took the leap early last year and landed a gig in New York City. You'll now find her behind the bar at Dante, an Aussie-run bar with a focus on elegant, Italian-style cocktail classics in the heart of New York City's popular Greenwich Village. Last year, Dante was recognised as number 16 on the World's 50 Best Bars list.
Oster has served drinks in Australia, the US and Russia, but she's learnt that "as a whole, consumers are the same".
"I get asked a few more questions here because people hear an accent, but the Americans are so lovely," she tells news.com.au.
After growing up in Shepparton, Victoria, Oster studied sports science — but decided not a pursue the field as a career.
"The only thing I really liked about it was working with people," she said.
Instead, she turned her hand to mixology and bartending, a field where you develop such intimate relationships with your customers that it shares some characteristics with science after all.
"We are like psychiatrists," she says.
"One gentleman once got pretty serious with me and revealed about a brother he didn't know he had. And I thought, 'I don't think I'm qualified for this.'"
While the humble bartender becomes privy to all sorts of intimate conversations from customers at the bar, the age of binge-watching has brought with it new occupational hazards.
"Back in Melbourne, some customers were talking about Game Of Thrones and I was like 'You've just ruined everything for me,'" she laughs.
While spoiling a TV show is forgivable, Oster says she occasionally encounters obnoxious behaviours that are much harder to overlook.
Ultimately, impressing your bartender is pretty simple.
"I'm big on manners," Oster says. "Please and thank you. It's so little — but it's such a big thing.
"Also, take your turn. Some people think that the bartender won't notice you, but we see everything.
"We know who's first, even if we have our heads down.
"Trying to get attention is a no-no. We know when you came in — it's fine."
And a pointer for anyone visiting the US: "Make sure you tip."
While making a killer cocktail is a requirement of the job, Oster says it's more crucial to know how to read people.
"You can teach any human being to a make a drink. You can't teach them to interact with people," she says.
"You have to figure out what people want.
"You can't just shove a drink down people's throats — they're not going to have a great experience."
And while Oster's warm personality is always on show, she admits that being behind the bar at an establishment that can serve up to 300 people a night can become stressful.
"You have to stop and go, 'I can't let that affect other people around me.' You might be exhausted, but you have to be there to talk to people and make sure they have a great experience," she says.
The joy of the job, she says, is linking up strangers sitting at the bar as a kind of friendship matchmaker.
"My favourite thing is making everybody talk as a group, getting everyone to join in and have a chat," she says.
She has a dream to open her own bar one day.
"It could be here, it could be in Melbourne, but I want a great place to hang out on a Sunday arvo, with a relaxed, Australian vibe with US quality, where people can enjoy a nice cocktail outside, which is what I love."
While Oster takes her craft seriously, she rejects some of cocktail culture's more pretentious elements. Let's just say you won't see her donning a lab coat and goggles to make you a drink.
"We mix drinks, we're not curing cancer or anything," she laughs.