Okay, so you’re a procrastinator. That’s cool, but only when it affects you. There’s no better way to piss off the bride than being lackadaisical about sending back your RSVP card (or emailing or texting, whatever you kids do these days). Your reply impacts the seating chart, overall cost, and amount of food served, so the bride needs it, like, now. If you RSVP the day before, you’re just “that jerk,” but if you RSVP the day before and then decide not to come, you should pretty much avoid contact with the bride for the rest of your life (she won’t care if you were deathly ill). When each plate costs $80 or more, that missing family of four costs a fortune (and will definitely be noticed).
Photo Source: Askamydaily.com 
Creating the seating chart is not just a task on the bride’s to-do list; there's an art to it. Figuring out how to circumvent those awkward family feuds is a challenge, but avoiding a major catfight mid-dinner between an uber-conservative friend and a hippie cousin is crucial. Trying to find that perfect middle ground can take hours and hours of deep thought, and even then, there will likely be several high-risk tables full of randoms that hopefully get along. Once the seating chart is finally done, it’s done. If the bride decides to sit you next to someone you hate, don’t be high maintenance and ask to swap with someone else. I don’t care if she sits you next to your ex-husband (though that would be dumb on her part), keep your mouth shut and deal with it.
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Remember how plates are, like, $80 a person? Great, well that’s why it's never okay to bring a date on your own accord. Before the wedding, the bride scoured her list of family and friends, and she painfully narrowed it down to those who were important enough to be there. Apparently, you were lucky enough to make the list, but your random hookup or BFF was not. Unless you’re given a plus one, don’t bring someone. Not only is it rude (so, so rude), but they also won’t have a chair or anything to eat, and you can say goodbye to your friendship with the bride or groom.
Photo Source: Wedding-blog.gigmasters.com 
Not all weddings are created equal, so there's bound to be something that you don’t think is picture-perfect. Maybe you prefer beef over chicken, or wish the DJ played better songs. Or, maybe the flowers just don't go well together or the bridesmaid dresses arent your cup of tea. Well, guess what? The bride probably doesn’t care what you think, so keep it to yourself! As corny as it sounds, this is her day, and whatever choices she's made have been because she wanted things that way. You can choose red over blue for your wedding, but vocalizing your personal preference will get you on the fast track to an embarrassing public beat down.
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Even if you aren’t really close to the bride and groom, stuffing your face and then immediately dashing for the exit is just tactless. We all understand what it’s like to have a busy schedule, but if you can only stay for 30 minutes—dinnertime—decline the invitation. And don’t think that you can sneak out without the busy bride and groom noticing; they will notice, and they’ll be bitter about it for years. After all, to them, this wedding is not just a free meal!
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Before you go rambling on about being superficial and greedy, hear me out: it’s $80 a person, people! If you invite a couple to enjoy $160 worth of food—not including drinks—I think it’s reasonable to assume that you will at least get a gift card or a nice vase from your registry. This doesn’t mean that struggling families should spend their last $100, but they should be willing to get the couple something in return for an entertaining night.
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Great, you got a gift! B,ut you’re not in the clear yet. If you decide to opt out of a registry gift and go for a unique, personal gift, make sure it actually is one of a kind. Getting the bride and groom a toaster or a blender, when they’ve already registered for one, is annoying—and just gives them something else to worry about returning. On the other hand, if you know them really well and think an amazing piece of artwork will go well in their new home, then go for it. The moral of the story: make sure to check (and double check) the wedding registry before buying.
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When free booze is involved, I know it’s tempting to just inhale one drink after another, but it’s important to pace yourself. Getting drunk and loud will quickly get the bride’s attention—and not in a good way. No one likes the drunk uncle who stumbles around slurring his words and hitting on women half his age, so don’t be that guy (or girl!). If you can hold your liquor, fine, but if you are known for picking fights, falling over, throwing up, or passing out while drunk, contain yourself!
Photo Source: Wedinator.com