Emily Post created a guide on American manners called “Etiquette” in 1922. The book includes 33 pages dedicated to the proper way to conduct weddings. It contains advice that ranges from familiar and practical to incredibly outdated. Brides have been turning to this book for generations for wedding etiquette tips.

“To begin with, before deciding the date of the wedding, the bride’s mother must find out definitely on which day the clergyman who is to perform the ceremony is disengaged, and make sure that the church is bespoken for no other service,” she wrote.

She goes on to advise on other outmoded procedures: visiting the stationer for invitations, when “her mother consults his mother” and what “the most extravagant trousseau” ought to comprise.

Still, many traditions and expectations born of this punctilious era are still alive: the flower girls and ring bearers, the vows, the kiss, the “I do,” the cutting of the cake, the first dance and other reception festivities.

But perhaps not for much longer, said New York wedding planner Alyssa Alinato.

“Traditions that have gone absolutely out the window are smashing cake into someone’s face and a garter toss,” she said. “I don’t know how that was ever a thing. The bouquet toss is also out.”

In what surely must spell the final groan in the agonizing slow death of Post’s stationer, “save the dates” are also mostly a thing of the past, Alinato added.

“It’s stupidly expensive,” she said. “Only, like, 30% of my clients do it, and only to their older relatives.”

Other once-familiar marital sights in danger of dodo-ification: children, cake and the receiving line after the ceremony.

“I would say 90% of my weddings are zero children allowed. Cakes are hit or miss,” she said. “They’ll do doughnuts or a croquembouche. The receiving line outside the church takes like an hour and we have done away with that.”

The new, modern wedding etiquette is focused on the lovebirds themselves. “When it comes to wedding etiquette, I think everyone finally realized it’s about the couple,” said Alinato.

In November, New Yorkers Ben and Rachel Martin, both 29, celebrated their individuality, their interests and the activities that marry them together as a duo, with a joyfully geeky ceremony.

“When I started planning our wedding I wanted it to feel like us,” Mrs. Martin said. “I didn’t want it to feel super traditional.”

Nevertheless, they chose a seemingly traditional venue, Chelsea Square, a historic portion of the General Theological Seminary in Manhattan — although perhaps for less traditional reasons.

“The venue gave us Harry Potter vibes,” said Mrs. Martin, which the couple leaned into with a reception dinner in the Great Hall with guests seated at long tables.

“We like fantasy, and we also play Dungeons & Dragons, so we made our characters and painted them ourselves,” said Martin. Those characters, a half-orc, half-man and a fairy, became cake toppers.

“Cutting the cake with a sword was Rachel’s idea,” added Martin. “In the office, we have one of the swords from ‘Game of Thrones.’ We thought, why not?”

Other fantasy twists on traditional elements included cellists playing music from “Lord of the Rings,” scroll menus, limoncello served in potion bottles and the bride’s tattoos fully on display. Still, the Postians were nonplussed.

“When I told my mom we were gonna have a long table, she flipped out a little bit,” said Mrs. Martin. “She was like, ‘I’ve never heard of that. I don’t understand.’ I feel like that happens a lot. This generation of parents and people older than us have in their mindset that there are things you’re supposed to do at a wedding. I was so taken aback. Like, they are tables, who cares?”

Despite the conflict, it came together beautifully, they said, but perhaps only because they were in charge of their own finances. “Ben and I had to be like, ‘This is what we’re doing,’ ” said Mrs. Martin.

Still, they incorporated some decidedly yesteryear moments: a handfasting ceremony, vows, a first dance and breaking a glass.

While individuality now rules the big day, there is still a strict code of etiquette that guests should be expected to follow. Alinato summed it up simply: “It’s not your day, so sit down and shut up.”

“You wouldn’t believe the number of people who talk while the toasts are going on,” she said, noting that she recommends toasts, vows and dances to all of her clients. “People have side conversations, or are at the bar getting drunk. It’s not the moment.”

In other words, even at the most avant-garde of ceremonies, have a little decorum.

Playing by the new rules

Do

RSVP on time. “So many people do not respect that date,” said Alyssa Alinato.

Dress appropriately. “I swear to God, I saw a guy wear a trucker hat to a formal wedding once.”

Be respectful that it’s this couple’s day. “A lot of people make it about themselves. I’ve had people have family situations. They’ve asked me to ask for Mom to be removed.”

Make memories. “The parent dances are my favorite part of weddings. I hope they never go away. They literally bring a tear to my eye.”

Celebrate discreetly. “I’ve definitely had people going to the bathroom with some little powder situations, and get a little too rowdy. All of a sudden everyone is really sweaty.”

Bring a gift. “Duh.”

Don’t

Bring your kids. “When they say ‘no kids,’ bringing your kids anyway doesn’t fly anymore.”

Talk during special moments. “I don’t care if it’s a 35-minute, boring toast, you should be giving respect to the person with the microphone.”

Let your teenager get tight. “This 15-year-old kid stole a bottle of vodka, drank the whole thing and proceeded to almost die in the middle of the wedding. We had to get an ambulance and try to do that discreetly.”

Lean on Google. “Everybody goes on Google and they think, ‘Oh, this is what I should do.’ It has ludicrous advice. Get a planner.”