1 | Neglecting Thank-You Notes

Saying "thank you" in person upon receiving a gift or going to an interview often feels like more than enough gratitude. However, if you're not actually writing a thank you note after the fact, you're ignoring some pretty basic rules of social etiquette. And writing thank you letters isn't just beneficial for those on the receiving end: Researchers at the University of Miami found that expressing gratitude was associated with greater energy, alertness, and enthusiasm.

2 | Not Introducing People

We've all been there before: You're hanging out with a friend and you randomly run into someone you know and they don't. In your confusion or haste, you accidentally forget to introduce the two, both an etiquette faux pas and an awkward moment for all. Not introducing people can make everyone involved feel uncomfortable, or worse, make them feel like you don't think they're worth introducing. Luckily, all it takes is a brief mention of each person's name and how you know them and that uncomfortable situation will be a thing of the past.

3 | Assuming Someone Else Is Treating

It is often assume that if someone asks to go out to eat, it's their responsibility to pick up the check. Although this may have been true at one point, if you're going to lunch with a friend or even on a date, it's always your best bet to assume that you'll be going Dutch.

"You can't assume that someone else is treating you just because they've asked you to a meal," says Napier-Fitzpatrick. "Always take enough for your meal, and ask if you can help. If they say no, say thank you, or ask to pay for the tip."

4 | Not Offering to Clean Up When Someone Else Cooks

Just because you didn't cook a meal doesn't mean that you're absolved of all responsibility after the fact. On the contrary, not offering to clean up when someone else has cooked is akin to saying, "Hey, why don't you do some more work on top of the hours you just put in?"

While the chef may deny your offer to help with the dishes, it's always polite to at least ask. And if it's your spouse serving you a home-cooked meal, it's especially important that you offer up your services: One 2016 study from the Council on Contemporary Families found that inequality when it comes to housework can put a huge strain on relationships and can decrease overall satisfaction in a marriage.

5 | Arguing Online

The anonymity—or perceived anonymity—of online conversations can make even the tamest folks prone to arguing with their digital nemeses. In fact, research conducted by VitalSmarts found that, among 2,698 respondents, 88 percent believed that people are less polite on social media than in person. Worse yet, 76 percent of those polled said they had personally witnessed a social media fight.

While it may be tempting to tell your annoying neighbor, a humblebragging Redditor, or a Twitter troll why you're right and they're wrong, doing so is an undeniable etiquette faux pas, and, thanks to the nature of the internet, one that might follow you around for some time.

6 | Talking on the Phone in a Restaurant

We all have those phone calls we absolutely can't miss. However, if you're in the middle of dinner with friends or on a date, you should politely excuse yourself instead of taking the call indoors; no matter how noisy the restaurant you're at is already, it's undeniably rude to talk on the phone inside.

7 | Not Making Eye Contact

While it's always a little awkward to feel like someone's peering into your soul during a casual conversation, avoiding eye contact altogether is equally—if not more—uncomfortable. "Making eye contact when you're having a conversation with another person shows respect for that other person and shows that you have confidence," explains Napier-Fitzpatrick.

So, how much time should we be spending looking at the person we're talking to? "We should make it 40 to 60 percent of the time when we're talking to someone," Napier-Fitzpatrick recommends. "It makes you a better listener and it shows that you're interested in what the other person is saying."

8 | Inviting Extra Guests to Events Without Asking

"The more, the merrier" doesn't apply to every situation, unfortunately. No matter what the occasion, you should always ask your host before you bring someone along to an event who wasn't specifically invited, even if it's your significant other. And when it comes to weddings especially, there's never an excuse for bringing an uninvited guest; those meals are expensive, and wedding planners plan out seating charts and meal counts far in advance!

9 | Bringing Your Dog With You Everywhere

We get it: You love your dog, and you want them with you everywhere you go. However, actually bringing them with you to every event and occasion is a major etiquette blunder. Not only is bringing your pet to certain places like restaurants unsanitary and a potential safety hazard, but the onus also shouldn't be on other people to let you know that they don't want to dig in next to your dog. You should always assume that places aren't dog-friendly unless you have specific evidence to the contrary.

10 | Listening to Something Without Your Headphones in

Just because you forgot your headphones and you have a long commute ahead of you doesn't mean that everyone should be forced to listen to your favorite podcast. There are few things more disruptive to others than playing something at full volume in an enclosed space. When you find yourself sans headphones, opt for a silent activity instead, and resume your binge-watching when you're in the privacy of your own home.

11 | Being Late

We all run late from time to time, and that's totally understandable. However, being a consistently late person is one etiquette mistake you can't afford to keep making. "[Being consistently late] shows that your time is more valuable than their time. It's showing disrespect for the person you're meeting. It's a personality flaw, for sure, but it's also an etiquette flaw," says Napier-Fitzpatrick.

Thankfully, there are ways to stop making this mistake. According to research from UCLA, envisioning your task complete may help you accomplish it more effectively and in a more timely manner.

12 | Pointing at People

Yes, sometimes it's hard to identify the person you're talking about using descriptors alone. But with that said, pointing at people is still a serious social faux pas. This gesture makes people feel singled out and can lead them to assume you're gossiping about them, even if all you're actually doing is complimenting their outfit or mentioning how helpful they were on a recent work project.

13 | Replying All

Though it's generally nice to make people feel included, using the "reply all" feature isn't the way to do it. Considering that the average person receives a staggering 122 emails on a typical day, replying all when something isn't actually must-have information is nothing short of rude. When you forward a meme or other non-essential info via reply all, you're taking time out of every recipient's day and potentially even stressing them out because of it. According to a 2015 study published in the journal Computers in Human Behavior, checking email less frequently was a significant stress reducer for study subjects, so try to be a part of the solution and not the problem.

14 | Not Saying "Please" and "Thank You"

While "please" and "thank you" are part of most people's vocabularies by the time they hit their 30s, that doesn't mean they're using them anywhere near enough. If you want to be the most polite version of yourself, these expressions of humility and gratitude should be used every time you're asking for something or have received a courtesy from someone else, your S.O. included. In fact, research published in the Journal of Positive Psychology found that being in a relationship where gratitude was readily expressed was significantly correlated with increased overall well-being.

15 | Texting While Talking to Someone

"The person in front of you comes first," says Napier-Fitzpatrick. "If you're having lunch with someone, your phone shouldn't even be somewhere you should see it." And if you do have a message or call that you can't afford to miss while you're out with someone? "Your phone should be in your pocket on vibrate, and you should let the person know ahead of time that you might be taking a call and excuse yourself to do it," Napier-Fitzpatrick recommends.

16 | Not Following Up After a Date

Not every date you go on is going to be a winner. However, for those concerned about social etiquette, ghosting isn't an option, especially when you're well out of your reckless teenage years. Though one study conducted by Plenty of Fish found that 80 percent of study subjects had been ghosted, you shouldn't be one of the many people who ignores text messages instead of admitting the hard truth. Regardless of how the night went, follow up within 24 hours to let your date know that you'd either like to see them again or don't see things working out. It may be an uncomfortable conversation, but it's worth having.

17 | Not Bringing Something to a Party

While it's safe to assume that a host isn't expecting you to bring a prepared dish or enough wine for everyone at their party, showing up empty-handed to a party is a major etiquette mistake. If you've been invited to an event, bring something to show your gratitude—something like a bottle of wine, a bouquet of flowers, or just a fun little gift for the host.

18 | Assuming Your Children Are Always Welcome

Many parents find their children endlessly delightful. Unfortunately, though, not everyone feels that way, particularly when a child shows up somewhere uninvited. So, before you decide that your little ones are welcome guests at any event, make sure you ask first, or you'll risk not being on the invitation list in the future.

"You should never assume that your children, your dogs, or cats are invited. There are as many people who want children at events as those who don't," says Napier-Fitzpatrick. "Don't be upset if they're not invited. It may not be a party for children."

19 | Tipping Too Little

While people from other countries may be appalled by America's forced-tipping culture, that doesn't mean that you can skip it here in the States. Unfortunately, plenty of people still skip the gratuity, however; in fact, according to a study from CreditCards.com, 20 percent of those polled said they don't tip when they go out to eat. Your server is counting on that money—they have bills to pay, after all—and, considering that virtually every restaurant in America assumes their employees will be tipped, there's no excuse for feigning ignorance about the total cost of your meal.

20 | Forgetting to RSVP

If you receive an invite to an event—on Facebook or otherwise—it's essential that you RSVP in a timely manner. Even if it seems like a relatively casual gathering, you're making the host's job harder by making them guess how many guests they can expect and thusly how much food or drink they should buy. If there's a formal RSVP card, make sure you mail it back with as much information as is requested as soon as you have an answer. And if you're RSVPing digitally, make sure you know The Single Best Way to Sign Your Emails.

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