There's not much you can do except slip on noise-canceling headphones and offer a sympathetic look to the parents, who already realize that the sobbing is disturbing everyone on board.

Giving up seats

Stand up for pregnant women, young children, the elderly and anyone with a physical impediment.

Bringing food

Is it smelly or messy to consume? Never a good idea in close quarters.

Exiting efficiently

To avoid a pushy logjam in a plane aisle, don't get up until the person in the row ahead of you has left her seat.

Manners for evenings out

Getting the bartender's attention

Make eye contact and smile. Tip well for the first round so that he'll check in with you later. What not to do: snap your fingers, flash a wad of cash or do the hailing-a-taxi salute.

Squeezing past people 

In a theater row, face the stage so that if you lose your balance, you can grab the back of the seat in front of you, not topple onto a stranger. When people scoot past you, stand up so that the seat folds up, then step back. However, if the show is under way, just move your legs to one side.

Cellphones 

Off the table at restaurants, and turned off and put away at the theater. Don't assume that you can sneak a peek. The glow of the screen distracts others in the audience. Skip the public shaming. Alert an usher and let him handle it.

Critiquing the performance 

Hold your two cents until you're safely away from the theater. Family or friends of the performers may be nearby.

Smartphone syndrome

In a world where condolence tweets (hashtag #RIP) have become commonplace, is it any wonder that smartphones and social media have opened a can of etiquette worms? "We tend to get overly comfortable because of the ease of using our devices," says Gottsman. In the interest of helping you clean up your highly wired act, listed (and corrected) below are some of the most flagrant breaches of digital decorum.

Posting about a night out when others weren't invited

It's bound to happen occasionally, but try to be mindful of people's feelings and think before you post.

Group texting

Refrain unless it's necessary to address several people at once. Otherwise reply only to the sender without dragging along the whole crowd.

Pressuring others to reciprocate a follow

Every follow is a judgment call, and you need to determine if it's a good fit for you -- as do others.

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