Should you tip your French waiter? Here's what to know ahead of Paris Olympics.

Americans are often unclear on when to tip stateside, let alone what customs apply in France. So as they prepare to join the 15 million people around the world traveling to Paris for the upcoming Olympics, some U.S. tourists could use a primer on tipping etiquette in the City of Light.

While changing tipping norms at home can leave American consumers frustrated over ubiquitous gratuity prompts, a completely different set of unspoken rules govern tipping expectations overseas — and some French restaurant operators may be eager to take advantage of foreigners' ignorance.  

At restaurants in France, bills automatically include a service fee of 15% to cover servers' wages, so waitstaff there are typically far less dependent on tips to earn a living wage, as they are in the U.S. Instead, it's up to the discretion of the patron to decide if the service was good enough to warrant an extra gratuity of a couple Euros, referred to as a "pourboire" (literally meaning "for drink").

Another cultural difference: All manner of service people, including waiters and salespeople, are often less solicitous of customers than they are in the U.S., in part because good service doesn't invite the same kind of monetary reward as in the U.S. In other words, don't expect your waiter to introduce herself by name, American-style — or to serve your food with an ingratiating smile. 

"The expression of service is not necessarily fast and attentive like it is here in U.S.," said Erika Rodriguez, an operations specialist at travel site Going.com, who has spent the past four summers in France. "That's not to say it's a bad experience, but they want to make clear they are not your servant. They are very direct." 

Are restaurants taking advantage?

It's no secret that European establishments often prefer Americans over other nationalities of tourists precisely because they're inclined to tip. And some visitors to France report that restaurants are trying to squeeze extra cash out of tourists by encouraging them to leave the kind of gratuity they would in the U.S. 

The trick was so common in St. Bart's the last time she visited, that travel guru Melissa Biggs Bradley, founder of the Indagare travel agency, referred to it as "the St. Bart's scam." 

"All the restaurants were asking people if they would like to leave tips without acknowledging that gratuity is built in," Bradley told CBS MoneyWatch.  

Going.com's Rodriguez noted that in Paris, that tactic is more common in touristy spots than at restaurants that mostly draw locals. "They bring you a credit card machine with suggested tips comparable to amounts you leave in the U.S.," she told CBS MoneyWatch.

Bending the rules

While that is hardly illegal, experts say it does amount to taking advantage of diners who are unfamiliar with foreign customs. 

Brian Warrener, who has researched tipping norms across Europe and how they differ from those in the U.S., said that at some restaurants in France he detected what he called "a little bit of a bending of the rules."

"Especially in places where lots of Americans are traveling, restaurants will include a line on the bottom in English saying tipping is not included, even though there's a 15% service charge," Warrener told CBS MoneyWatch. "So they are clearly trying to communicate to folks who may not know the tipping norms in France."

He noted that some operators use tablets to accept payment that include prompts for tips of 15% to 30%, a practice he suspects is becoming more widespread in anticipation of visitors arriving in Paris for the Olympics. 

"In the U.S., that would be an inflated tip, but in France, where tipping is not part of compensation, it's taking advantage," Warrener said.

Bradley of Indagare offered advice for avoiding such tipping ruses. "If you pay by credit card and are prompted to leave a tip, ask if service is included," Bradley said. 

Be forewarned: "They might try to fudge it, but they can't say 'no' when it is. They could say it's a question of whether or not you want to give me something for nice service. But it's absolutely standard, so the assumption should be you're paying the service," she added.

How much should I leave at a restaurant in Paris?

Given that a service charge is already baked into the total cost of a meal, servers aren't expecting a whole lot extra. But it is common to leave some loose change if you're getting a coffee or meal in reward for good service. For example, rounding up a bill from 13.50 Euros to 14 Euros, or leaving a few Euros, is usually sufficient.

"What Europeans are accustomed to doing when they get good service is they'll round up the bill to say, 'Nice job, here's a little something extra,'" Warrener said. 

He adds that, as a general rule, it's incumbent on tourists to familiarize themselves with other countries' customs before jetting overseas. 

"If you go to France and don't understand the tipping culture and assume it's like it is in the U.S., they're making it easy for you to make a mistake to their benefit," he said.