Based on David's question about what things to avoid and things to be mindful of, here's a open ended list of Do's and Don'ts in no particular order:
DO take off shoes when entering certain places.
Where and when to wear shoes, slippers, or only socks/bare feet can be a bit confusing at times. If you're not sure, just ask.
Shoes come off just inside the door. You will typically put on slippers as you enter.
I HIGHLY RECOMMEND having slip-on shoes. Japanese people will literally walk into their shoes and keep going. If you need to tie your shoes it is likely you will not have a place to sit when you do!
There are different slippers for the house and for the toilet!
Change from house slippers to toilet slippers before entering the toilet.
Leave your house slippers outside the toilet door. Be sure to not walk away with toilet slippers on.
Never step outside with house slippers on, not even for a second! Sometimes there will be "outdoor slippers" for conveniently going out to the car for something you forgot or to hang laundry on a clothesline, for instance.
In some public places like restaurants, you may be able to put your shoes in a cubby hole or even a small locker.
Where to take off shoes and put on slippers:
AirBNBs (Socks/bare feet optional)
Private residences
Onsen (hot bath) changing/locker rooms.
Temples and shrines when entering particular rooms
Hotel rooms
Some restaurants especially floor seating tables. If Tatami mat, then only socks/bare feet (See below). The host will typically indicate where to take off shoes if it's not obvious.
Where to wear only socks/bare feet
"Tatami" rooms/mats. ALWAYS remove your slippers before stepping on tatami mat as they are easily damaged.
DON'T do whatever you're doing if someone gestures with their arms crossed in front of their chest. This is the non-verbal sign for "forbidden." For example, you may have a shopkeeper do this if she sees you taking pictures of her clothing designs, or you are entering an employees-only area.
DO understand basic non-verbal gestures. Japanese relies much more heavily on non-verbal gestures and guttural sounds, which is good in one sense since it can help bridge communication with non-English speakers. Still, it's only good if you understand these non-verbal symbols. Without listing a bunch here, ones to avoid include pointing to others, pointing at food with chopsticks indecisively (especially from shared plates), or making too much eye contact. Here's a good article on non-verbal cues and gestures: https://www.fluentu.com/blog/japanese/japanese-gestures/
DO stand or walk to the left and pass on the right. Just as the Japanese drive on the left side of the road, they also walk on the left side of the sidewalk or passageway, or when on stairways. When standing on an escalator (and we will often), stand to the left and allow people want to walk up the escalator to pass on the right.
DO stand in the appropriate spot for your train when waiting on the platform. The train system is very efficient, and part of the efficiency depends on passengers cuing up in the right place for their train. Different trains will have their doors staggered so that people waiting for one train will wait in one spot, while people for different train will wait in a another spot. These may be color-coded lines on the platform floor, or overhead signs. There are also lines to show where people on line should stand. On reserved trains (like the Shinkansen) there will also be locations for your seating section on the train so you enter at the correct car. People do not cut each other once the train door opens, but maintain their place in line as they enter.
DO take a clean tray and pair of tongs at a bakery, pastry shop or coffee house. Never pick up the baked goods with your hands. Bring the tongs with you to the cashier, who will collect them for cleaning. You see this in the US sometimes as well, but you will see more often in Japan, even at 7-11 stores.
DO pay at the cashier or front desk at restaurants. With rare exceptions, you never pay at the table at the end of a meal no matter how fancy or upscale the restaurant is.
DON'T begin eating without saying "Itadakimasu," (pronounced E-tadaky-mas) which is the equivalent of "bon appétit." At the end of a meal, we say "Gochisousama" (Go-chee-sow-sa-ma), especially to someone who cooked or served the meal, like a chef or host. When toasting, we say, "Compai!" (Kom-pie).
DON'T pour your own drink (unless you're alone). Whether it's tea, beer, sake or water, it is customary for others to pour your drink, and then for you to reciprocate.
DO lift bowls of rice, noodles, and small plates off the table to make eating with chopsticks easier. Also, soup in a small bowl is sipped as from a cup and never eaten with a spoon. Use your chopsticks to eat any solid bits like tofu or nori (seaweed) that may be floating in the broth.
DON'T stick your chopsticks into food and leave them standing (especially rice) -- this is a funeral ritual, and considered rude, even morbid.
DON'T double dip sauce at the kushiage (aka Kushikatsu) counter: Kushiage is deep fried food on a skewer, and we will definitely be indulging at least once in Osaka. There will be a container of sauce to dip into, but for hygene's sake, you get one chance to get sauce once the skewer is lifted from your plate. Even if you don't bite it, if you put it back to your plate, you shouldn't dip. There will be signs saying this, but they will be in Japanese. https://gurunavi.com/en/japanfoodie/2015/09/kushiage.html
DON'T tip. Tipping is not a custom in Japan under any circumstances: restaurants, taxis, delivery. Since you never pay at the table, there is no expectation to leave money on the table, even coins (as one might do in Europe).
DON'T expect to find trashcans very easily. People are expected to take their trash home with them. Trashcans can be found in convenience stores like 7-11 and coffee shops, but they are almost non-existent on the streets. If you buy a drink or snack from a stand or small shop, the shopkeeper will usually take the trash after you are done if you ask. Vending machines usually have a recycling bin attached or nearby.
DO separate your trash EVERYWHERE. In general, trash is separated into four categories: 1) Metal and glass, 2) PET (plastic), 3) Paper and Cardboard, and 3) Combustibles (aka everything else). Japan is very efficient at recycling They don't have landfills; what they can't recycle, they burn and recoup the energy. Labels on metal/PET/glass containers are usually perforated and removable. They should taken off and placed with the combustibles before put the container in the recycle bin. You can read more details here: https://www.japanlivingguide.net/dailylife/life/recycle-symbols/
DO spend your coins first! Banknote denominations start at ¥1000, which is the equivalent of a $10 bill. When you break a ¥1000 bill to spend ¥100 (about a dollar), you will get all the change in coins. There are ¥500 coins, but often you will get 9 ¥100 coins. Do that twice without reaching for your coins first and you will be weighed down with coins very quickly.
Tatami = Socks or Bare Feet ONLY!
