1RSVP by the date requested.
Getty ImagesNo exceptions. "The couple needs to know your attendance by that date so they can finalize details, such as the catering order and the correct number of chairs," says Lindsey Nickel, wedding planner for Lovely Day Events. Plus, it's time-consuming for the couple to track people down.
2Don't assume you get a date.
Getty ImagesOr that your kids can come! Your invitation will indicate who's welcome, says Melanie Tindell, owner of Oak & Honey Events. If you are given a plus one, put your guest's name on the RSVP card. "This way, the couple can include his or her name on the guest list, escort cards, and any other printed materials," she says.
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3Stick to your RSVP response.
Getty ImagesIf you said months ago you're attending solo, but recently started seeing a great guy, don't call the bride to change your count. "The amount of work you just created for your friend, between calling the caterers, event venue, rental company, adjusting seating charts, is immense," says Christy McDougal, a wedding planner at The Elm Estate.
4And NEVER bail.
Getty ImagesYou might think no one will notice your absence, but it's actually quite obvious. Whether it's your name card still sitting near the entrance or your salad being carried away by the staff, the bride and groom will find out if the meal they paid for went untouched, warns Lisa Mark and Rebecca Lozer, co-hosts of The Secret Life of Weddings Podcast.
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5Never wear white.
Getty 6Don't show up early.
Getty ImagesArriving earlier than 30 minutes prior to the ceremony could throw off the hosts if they're not ready — and be downright awkward. "It's better to wait in your car than go into the venue and risk stressing out the bride by seeing her before the ceremony," says Holly Patton Olsen, founder of Perfectly Posh Events.
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7And especially not late.
Getty ImagesIf you can't get there at least 10 minutes prior to start time, you are better off not showing up. "Walking in as the bride (or groom) is walking down the aisle in incredibly rude and ruins video and photos that are being taken," says Brandi Hamerstone, owner of All Events Planned. Plan for traffic and parking ahead of time.
8Always give a gift.
Getty ImagesBut don't stress if it's not huge. Jodi RR Smith of Mannersmith Etiquette Consulting says you should give based on your budget and relationship to the couple. "A second cousin returning home from the Peace Corps is going to give a more modest gift than a well-to-do neighbor with a flourishing business," she says.
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9Only bring cards to the reception.
Getty ImagesMany venues and planners won't accept responsibility for gifts due to liability, so a family member will have to collect them after the reception. "You may bring a nice congratulatory card, but always ship your gifts to the couple in advance of the wedding day so they have one less thing to worry about," says Michelle Garibay owner of Michelle Garibay Events.
10Put your phone away.
Getty ImagesMore often than not, the couple hires a photographer to capture their big day — and nothing ruins a picture perfect moment more than your big phone in the middle of the shot. "Save selfies for the dance party and leave the important pictures to the pros," says Kimberly N. Rhode, owner of Hitched Events.
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11And stay away from social media.
Getty ImagesPosting a picture of the bride or groom before being getting the go-ahead steals the thunder from the couple, explains Mark and Lozer. This is especially true for the bride, who puts a lot of time and thought into her look for the day.
12Let the couple eat in peace.
Getty ImagesSince wedding days are often long and sometimes stressful, one of the few moments the couple has together is during dinner. "If a couple takes the time to sit for 15 minutes to eat their meal, let them — it very well could be the first thing they have had to eat since morning," says Ashley Craker, owner of Ashley Marie Wedding Solutions.
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13Don't complain about the food.
Getty Images"For those guests with dietary restrictions or food allergies, be sure to let your host know on the RSVP card," says Daulton Van Kuren, owner of The Refined Host. "This way, the couple can inform their caterer and make special arrangements for you." If you forgot to do this until the night of, talk to the waiter or suck it up.
14Only toast with permission.
Getty ImagesWedding planners and couples often create a day-of schedule and hand-select speakers, so if an unannounced toast happens, it can throw the entire night off, warns Emore Campbel, owner of Emore Campbell Events.
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15Pace yourself when drinking.
Getty ImagesEven if champagne is everywhere you turn, make sure you don't go over your limit — if not for your own embarrassment, for the bride and groom's. "I've seen videos where I just hung my head watching drunk guests totally ruin the video," says Michele Velazquez, owner of Pop the Knot.

Lauren is a senior editor at Hearst. She was previously the senior editor at WomansDay.com and the home editor at GoodHousekeeping.com and HouseBeautiful.com. Her book club, ramen, and jean jackets are a few of her favorite things.
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