The etiquette nobody writes down.
Rice on the left, soup on the right. No smoking on a plane. The unspoken rules people expect you to already know: by country, by situation.

Category
Country
94 rules
All rules
Accept the refreshments at a business meeting
PhilippinesBusiness
Accept the second offer of food, not just the first
IndiaHome
Always queue, never cut in
United KingdomSocial
Always say "Bonjour" before anything else
FranceSocial
Arrive a few minutes early for a meeting
GermanyBusiness
Arrive a little late, and bring a gift
MexicoHome
Ask about shoes, and accept the tea when it's offered
United KingdomHome
Avoid black or white gift wrap
ThailandGifts
Avoid gift sets of four or nine
JapanGifts
Avoid leather and white-wrapped gifts
IndiaGifts
Avoid sets of four, knives, and clocks
KoreaGifts
Bow and use two hands with seniors
KoreaBusiness
Bring a small gift when visiting someone's home
KoreaHome
Bring back omiyage after any trip
JapanGifts
Build rapport before getting to business
MexicoBusiness
Buy your round at the pub
United KingdomDining
Check tattoo policy before visiting an onsen
JapanTravel
Cover shoulders and knees before entering a temple
ThailandTravel
Don't ask for parmesan on seafood pasta
ItalyDining
Don't flip the whole fish over
ChinaDining
Don't mistake directness for rudeness
GermanySocial
Don't open a gift in front of the giver
KoreaGifts
Don't order a cappuccino after 11am
ItalyDining
Don't schedule business around Friday or prayer times
Saudi ArabiaBusiness
Don't sit down until you're shown your seat
ChinaBusiness
Don't take phone calls on trains or buses
JapanTravel
Don't tip
JapanDining
Dress modestly, and don't initiate contact across genders
Saudi ArabiaSocial
Dress well even for a quick errand
ItalySocial
Eat and pass food with your right hand only
IndiaDining
Eat with the spoon, use the fork to push
ThailandDining
Exchange business cards with two hands
JapanBusiness
Give flowers in odd numbers, unwrapped
GermanyGifts
Give gifts with both hands, open later
PhilippinesGifts
Greet elders with nginge'
GuamSocial
Greet friends with la bise, not a hug
FranceSocial
Greet the most senior person first
IndiaBusiness
Greet the oldest person in the room first
VietnamSocial
Greet with a handshake or a single cheek kiss
MexicoSocial
Greet with a wai, matched to who you're greeting
ThailandSocial
Greet with namaste, and touch elders' feet
IndiaSocial
Hold eye contact during a toast
GermanyDining
Keep the fork in your left hand, knife in your right — even for pizza
BrazilDining
Keep your hands on the table
FranceDining
Keep your hands visible, and don't rush off after eating
MexicoDining
Learn to hear the disagreement inside the politeness
United KingdomBusiness
Let the eldest or the host eat first
PhilippinesDining
Let the host toast first, and clink lower
ChinaSocial
Let them lead the cheek kiss, and match the local count
BrazilSocial
Let your host offer food more than once
GuamDining
Never criticize someone in front of others
ChinaSocial
Never give a clock as a gift
ChinaGifts
Never give chrysanthemums, and count your flowers
ItalyGifts
Never leave chopsticks standing upright in your rice
VietnamDining
Never smoke on a commercial flight
GlobalTravel
Never speak ill of the monarchy, never step on money
ThailandTravel
Never stand chopsticks upright in rice
JapanDining
Never touch a latte stone, and keep your voice down
GuamTravel
Never touch someone's head, or point your feet at them
ThailandSocial
Never write a living person's name in red ink
KoreaSocial
Number 4 is unlucky, 7 is lucky
KoreaSocial
Place rice to the left of soup
KoreaDining
Present and receive business cards with both hands
VietnamBusiness
Present business cards with both hands
ChinaBusiness
Print a Portuguese translation on your business card, and don't step back
BrazilBusiness
Put bread directly on the tablecloth
FranceDining
Reciprocate favors with chenchule'
GuamSocial
Remove your shoes, and don't wander past where you're invited
PhilippinesHome
Respect Ruhezeit — quiet hours are enforced
GermanyTravel
Shake every hand, use titles and last names
ItalyBusiness
Shake hands in business settings, skip la bise
FranceBusiness
Shake your cup to signal you're done with the coffee
Saudi ArabiaDining
Show up around 20 minutes late — showing up on time can catch your host off guard
BrazilHome
Skip chrysanthemums and even numbers when gifting flowers
FranceGifts
Skip knives, clocks, and handkerchiefs as gifts
VietnamGifts
Skip lilies and chrysanthemums, wrap it well
PhilippinesGifts
Skip marigolds as an everyday gift flower
MexicoGifts
Skip purple wrapping and sharp objects when giving a gift
BrazilGifts
Skip white flowers, red ink, and shoes as gifts
KoreaGifts
Slurping noodles is polite, not rude
JapanDining
Stand on the correct escalator side
JapanTravel
Take off your shoes, and let your host seat you
Saudi ArabiaHome
Take off your shoes, wear the slippers you're given
ChinaHome
Take your shoes off entering any home
KoreaHome
Take your shoes off indoors
JapanSocial
Take your shoes off just outside the door
VietnamHome
Take your shoes off, and bring a small gift
GuamHome
Turn away when drinking with elders
KoreaSocial
Use "po" and "opo" to show respect
PhilippinesSocial
Use a title or honorific, not a first name
KoreaSocial
Use your right hand for eating, greeting, and giving
Saudi ArabiaSocial
Wash before soaking, and keep your towel out of the water
JapanTravel
Weather is always safe small talk
United KingdomSocial
Wrapping matters as much as the gift
JapanGifts