4 mistakes to stop making at high-end restaurants, according to an etiquette expert

When dining at a high-end restaurant, patrons should expect to receive a higher level of service. For this reason, Swann said it's important to build rapport with the wait staff.

In the past, "I've heard people say, 'don't interact with waitstaff,' and that's incorrect, and I think that's quite snobbish," explained Swann.

"Instead, you should communicate effectively with the staff, find out their name," she told BI.

She also suggested calling the server by name when making specific requests or asking questions about the menu. According to Swann, this can help set the tone for an enjoyable dining experience.

According to Swann, another common mistake diners make is dressing inappropriately.

"You might live in an area where the attire is more casual and shorts are acceptable, but that may not be acceptable in some higher-end restaurants," she said.

To avoid this faux pas, she recommends finding out the dress code in advance to ensure you're appropriately dressed.

To do that, "You can check the website or call ahead," she said. "And then another thing that I encourage people to do is look up photos."

For example, Swann recommends looking up the restaurant's social media pages to get an idea of what appropriate attire may look like. She also suggested looking at the restaurant's hashtags to see what other people who have dined there wore.

Swann said another mistake guests tend to make at high-end restaurants is showing up "fashionably late." In fact, she said showing up on time helps to ensure the service goes as planned.

"The service at the high-end restaurant is based upon everyone being there at the same time, on time," she said.

According to Swann, being late can impede the flow of the service.

"It's important to respect people's time. When someone gives you a time to show up, they're expecting to start within the flow they have designed. And It's quite disrespectful to show up late," she said.

"You should always leave a tip at every restaurant you dine at, regardless of if it's high-end or your standard mom-and-pop restaurant," Swann said.

However, she noted that although 20% of the bill is the standard tip at a regular restaurant, the tip at a high-end restaurant should be a minimum of 20%.