In America, no matter who you are, you have to tip.

It’s not always our favorite practice, and sometimes, an extra 20 percent seems totally unwarranted—but skipping out on tips is a faux pas at best (for instance, not tipping a hotel bagboy), and an incredible act of rudeness at worst (not tipping your waitress).

“It’s often said a tip is not an obligation,” says national etiquette expert and founder of the Protocol School of Texas, Diane Gottsman. “But we have to remember for those in the service industry, providing the service to us is an obligation. And we are expected to leave gratuity for good service.”

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There’s also a whole world of service workers who are often left out of the tipping conversation. Pretty much everyone knows that restaurant workers rely on tips, but don’t forget about other service workers who need gratuities to get by.

We spoke with Gottsman and several service industry workers to try to clear the air. Here’s what you need to know to tip appropriately—so the next time you’re out, you can be the voice of reason.

To tip, or not to tip; that is the question.

We’ll start off with the obvious: You should always tip your restaurant servers. This means everywhere, from a small cafe all the way up to fine dining. The amount servers expect may vary somewhat, but if you’re not tipping the waitstaff, you’re making a big mistake.

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“If I don’t get tipped, I’m basically working for free,” says Lucy, a 31-year-old waitress from St. Louis. “Well, not really—the employer is supposed to make up the difference between minimum wage and what I actually get during the off hours, but that doesn’t always happen.”

“Just because it’s a really expensive restaurant … we should not skimp on the tip,” Gottsman tells Urbo. “If you can afford to go someplace, you should be able to be comfortable leaving the tip as well.”

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The same should be said for the opposite situation. Your bill in a coffee shop might seem small, but you should still leave a dollar or two. After all, there’s a tip jar on the counter for a reason.

“I don’t really rely on tips, simply because it’s so unpredictable,” says Nick, a 28-year-old barista. “Still, it’s appreciated. There have definitely been a few weeks where tips helped me cover my bases.”

Hair stylists and salon owners also rely on gratuities—some more than others.

If you visit a specialty salon, your stylist most likely pays rent to have a space. That means that, even if your cut and color add up to a couple of hundred dollars, they still benefit from—and expect—a tip.

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That might also be true for salon owners. Years ago, owners typically declined tips, but this has changed, says Gottsman.

“Today, if you asked any salon owner, they are going to say they appreciate gratuity,” she says. “It might be their salon, but they still have rent.”

Tattoo artists are in a similar boat as stylists.

Many artists pay a “booth fee” to the shop, plus they personally purchase all the machines, needles, and inks—not to mention all the time and effort that goes into crafting a unique, personal piece of artwork. The $300 you spend on a tattoo doesn’t just all go into the artist’s pocket, but your tip does.

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“Tips are a big part of my income,” says Tom, a 35-year-old tattoo artist. “If I don’t get a decent tip, I assume I did something wrong…or that the customer’s a [expletive].”

That’s frank but fair.

When traveling, don’t forget to tip your housekeepers.

People tend to overlook housekeepers, but without them, every hotel room would be an absolute horror show. Tip them.

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We should note that hotel housekeepers are back-of-the-house staff, so salaries in those positions aren’t set with the expectation of tons of tips coming in, per CNN. A Cornell University School of Hotel Administration survey found that only 30 percent of guests in U.S. hotels leave housekeeping tips. Still, if you leave a few bucks per day for your housekeeper, you’re showing respect to some of the hardest working people in the travel industry.

“[Leave] $2-5 a day,” recommends Gottsman. “And make sure you write a note. You want to make sure they’re not concerned that it’s going to look as if they’re taking it.”

Another misconception is that you don’t have to tip rideshare drivers.

“People avoid tipping, even though now it’s on the [ridesharing services’] website, and it’s on their app. But they should be tipped the standard 15 percent of the fair, as well,” says Gottsman. Rideshare companies take a hefty chunk out of the driver’s pay, and a lot of money goes into vehicle upkeep.

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Other people that need tips include delivery drivers, movers, and other non-salaried workers who deliver something—anything—to your house.

When in doubt, remember the basic rules of tipping.

So, how much should you tip, provided that you’ve determined that a tip is necessary?

… what you’re doing is you’re being respectful to the people who are providing a service.

“You’re looking at about a 15-20 percent gratuity across the board for almost all services, except in the food industry, whose standard is 18-20 percent,” Gottsman says. This sliding scale allows for some wiggle-room depending on each specific interaction and situation.

When it comes to services that movers or housekeepers offer, you should pay attention to what they actually have to deal with.

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“Do you have a large amount of furniture, and are the movers staying there all day long, going up and down flights of stairs? You might give them a little more of a tip than normal,” Gottsman tells Urbo. All of these things should factor into how you tip. “Because what you’re doing is you’re being respectful to the people who are providing a service,” she says.

For services that may be “free,” like valet parking or a bellhop service at a hotel, Gottsman recommends paying a few dollars.

Make sure you don’t have misconceptions about tipping etiquette.

When you combine confusing social expectations with people’s actual income, you’re bound to spawn a lot of myths. People have some weird ideas about tipping.

“One misconception is if you spend a lot of money on a service or in a restaurant, [people think] they don’t want to tip as much because they think they’re already paying,” says Gottsman. “But the servers aren’t getting that. Plus, there might be multiple people sharing that tip.”

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Another issue: Some people think they don’t have to tip if it takes a long time to get their meal or if they don’t like their server.

Well, first, know that a long wait usually isn’t the servers fault. You can talk to the manager about that, says Gottsman, but don’t stiff the server. And if the server is rude, start with compassion—don’t go straight to skipping the tip.

”You might try and defuse the situation by saying, ‘Are you having a particularly tough night?'” Gottsman says. “Try and soften [the situation], so it changes their attitude, or you can leave 10 percent and talk to the general manager.”

In any case, it’s never a good idea to go below 10 percent.

“It’s in bad taste,” Gottsman says. “It’s a poor reflection on you.”

Some people don’t get tipped (even if they seem like they should).

If someone makes a decent salary, then you’re off the hook for leaving a tip.

But we don’t know what we don’t know. We want to do the right thing, we’re just not quite sure.

“You’re not going to tip your doctor. You’re not going to tip your lawyer. You’re not tipping somebody in the medical field, let’s say a nurse,” says Gottsman. “Now, you might bake them a big basket of muffins to say thank you for something they’ve done, but they do not require a tip.”

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It’s important to learn when a tip is appropriate and when it’s not. Knowing how to navigate gratuity properly will help avoid any awkward situations—but you have to push through some awkwardness to gain that understanding. That means offering tips and having them refused.

“It feels off,” says Gottsman. “But that’s what etiquette is all about. It’s about making people comfortable to know how to deal with awkward moments.”

“They will say, ‘okay, that was weird,’” continues Gottsman. “But we don’t know what we don’t know. We want to do the right thing, we’re just not quite sure. So [etiquette] is about taking those weird moments away and just knowing.”

In other words: When in doubt, tip service workers a few bucks. Tip 15-20 percent on any sizable bill, and if there’s no bill, toss in a couple of bucks.

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“Nothing’s quite as frustrating as working hard all night only to realize that I’m going home with loose change,” says Lucy. “Working in the service industry opens your eyes. I’d say, even if you’re getting bad service, even if you didn’t like your meal or your ride showed up late—whatever’s going on, tip. It’s part of the service, not really a gratuity, and if you can’t afford it, don’t depend on service workers.”