Etiquette. It's an old-fashioned word, suggestive of fish knives and finishing schools, and hardly relevant to life in the digital age. Wrong.
A new book by the American manners expert Caroline Tiger argues that, with more people living in closer proximity, and ever more opportunities to embarrass ourselves online, the need for rules has never been greater.
So she has written a handbook for modern living, How to Behave. Published in the UK this month (by Quirk Books at £10.99), it offers advice on how to deal with situations that previous generations of etiquette experts could never have dreamed of.
How to "defriend" a colleague on Facebook; what not to write in a round-robin email; the rules of "sweatiquette" at the gym.
Like most rules of etiquette, much of it is simply common sense and designed to make social interaction more pleasant. But it needs spelling out, says Tiger, "because modern society enforces so few rules".
Here, The Independent selects a dozen of her tips:
At a concert
No singing along with the soloist, whatever the type of concert (unless, of course, it's a sing-along). At a classical concert, refrain from clapping until the very end of the piece - not after each movement. Lighters should be held high enough not to risk lighting a fellow concertgoer's hair. No impromptu air guitar solos.
Stay focused on the music. This will allow you to keep in your groove, as opposed to focusing on the people who are slamming into you (which may trigger some retaliatory instincts). Do not violate the women in the pit by taking advantage of the close, unmonitored contact to make inappropriate grabs.
Limit your time onstage to 20 seconds or less to avoid getting nabbed by security. That means no extended antics onstage, no excessive showing off for the crowd. Wear clothing devoid of hardware: remove piercings or spiked jewellery that could injure an audience member when you dive off the stage and into their arms.
At the cinema
When eating popcorn, retrieve it from the tub as noiselessly as possible. During a quiet scene, try sucking on it for a few seconds before masticating to minimise crunching. Do not slurp the last drops of soda through the straw when you get to the end, and refrain from chewing the ice. If you've seen the movie, refrain from reciting upcoming dialogue. Do not yell at or in any way attempt to communicate with the characters.
At the sales
Kicking, shoving, biting and hair-pulling are strictly forbidden. Whoever lays a hand on the item first gets first crack. Hiding items in racks where they don't belong so you can come back for them later is cheating.
At the gym
Sweatiquette: After use of a machine, wipe off your sweat. Do not just quickly wipe puddles - hold the towel in place for several seconds to soak up the reservoir of fluid.
At the beach
If someone applies your lotion, it's polite to return the favour. While applying lotion to an acquaintance's back, do so clinically, with light, short swipes, as opposed to long, languorous strokes. Don't use lotion-spreading as a pick-up line. That's so 1970s.
Social (and antisocial) networking
It's OK to ignore an unwanted friend request. When you defriend people, you need not notify them. Don't use any social networking account solely as a venue for self-promotion. Even if the page is explicitly for your company, your ratio of community-building to promoting should be about 80 to 20.
What not to post on Facebook
* Granular info about sex lives or bowel movements.
* Nasty passive-aggressive comments about your spouse or partner.
* Tags on a person in a photo who is having a bad hair day or is engaged in, or the subject of, any embarrassing activity.
* Photos from the delivery room.
* How much you hate your boss or co-worker.
Email and texting
The first back and forth with a person should include a salutation and a proper closing. "Yo" is never correct and hardly ever acceptable. Never use emoticons and acronyms when corresponding about a business matter. Outside of business, use sparingly.
Food you can eat with your hands
Corn on the cob.
Chips and salsa.
Dishes commonly mistaken for food you can eat with your fingers
Chicken drumsticks (use a knife and fork).
Spare ribs (ditto).
Prawn cocktail (use a cocktail fork).
Pastries (use a pastry fork).
Lobster (pull out the meat with a lobster fork).