I am aware that Japan has many unwritten rules of etiquette. What are some of the most common (and offensive) breaches of etiquette made by visitors?
On the flip side, what behaviors show respect and understanding of the Japanese culture?
Take name cards with two hands when given to you, give them with two hands. Look at the received card, put it in front of you on the table while you are talking to the person(s).
You CAN punch with one chopstick into food and hold it with the other if it's something hard to eat (dumplings, potatoes etc). Don't stick both in however.
Do not soak your sushi rice in soy sauce. Ideally, try to dip only the fish into it. Do not throw too much wasabi into the soy sauce. Ideally, just take of a small piece and put it directly on the fish before eating it. Those two rules are specially important if you are sitting at a sushi counter since both of the errors tell the chef that you need to "fix" his food. You CAN however eat sushi with your right hand if you have issues with chopsticks. Eat the pickled ginger between sushi pieces in small portions - do not gobble it up before the sushi itself arrives.
In general, try to mimic the behavior of the people that are of the same status around you (co-workers, co-students) when it comes to bowing, where to sit, how loud to talk, how much to drink/eat when in presence of someone superior (boss, professor etc).
Do not address yourself/introduce yourself with -san. While you say "this is mister Smith" and in Japanese say "this is Smith-san", you do NOT introduce yourself with "my name is Smith-san" but rather "my name is Smith".
Dragons are lucky creatures. Do not compare something bad/dangerous to a dragon. I have seen this some times and it really shows you have no idea about Asia at large.
If you try to speak Japanese, try on someone you trust to give you a good evaluation first. If you have a strong English/French accent and people do not understand what you want to say in Japanese, you make them feel uncomfortable. You can on the other hand make a really good impression by being able to make some short phrases that you can use to give positive feedback ("Oishkatta desu" after a dinner, etc) in a reasonably understandable accent.
Do not open gifts that you received in front of the person who gave them unless encouraged to do so. It makes you look greedy and there is a huge risk of face loss in case you do not like what you received etc.
If you have Japanese guests wherever you are, give them a small (toy/ceramic/whatever) frog as a departure gift. The word "frog" and "return" have the same pronunciation in Japanese and indicate that you want THEM to come back. Do not do that if you are at someone else's place.
If you go somewhere, buy a small souvenir (such as chocolates, cookies etc) from the place where you have been, specially local stuff stuff that normally cannot be bought in a supermarket everywhere. If you are in an office in Tokyo and go to Osaka for a business trip, buy some of the stuff sold at the train station. Those are always individually packed so you can give everyone in your department on cookie/whatever. Put those on everyone's desk when you return - no need to hand them over in person. It's not so important what it is, or that it's expensive. If you are on a private trip, buy something small for your best friends only - maybe your boss, too.
If you are in a restaurant, check if there is a cashier at the entrance when you come in. You will also most likely then have a paper on a clipboard at/under your table where the waiter notes down your orders. When paying, take that clipboard and go directly to the exit to pay. Otherwise, ask for the check on the table.
It's completely normal to ask which sauce goes with which food. Often Japanese people on the table will not know what goes with what either since many restaurants try to make it more special by adding different dipping sauces for a course.
You will most likely get 3 questions as a foreigner in Japan (in one row, asked from the same person): Do you speak/study Japanese? Do you like Japanese girls? Do you eat Nattō? I think this comes from some Japanese having a certain fear that they are not Japanese "enough". They feel they speak poorly Japanese, they often prefer/admire western women and many do not like nattō. If you study/like the Japanese language, fancy Japanese girls AND like nattō, you are almost more Japanese then they wish to be. I speak Japanese and I like Japanese girls, but I do not like nattō. Japanese people were ALWAYS relieved when I told them I do not like nattō.
Do not bring up topics about WWII or the island disputes with Korea/China etc. If the topic is there already, do not comment on it. If you feel you need to contribute or participate, bring an example from history/territorial disputes in your country, but do not give opinions about the Japanese topics. Chances are high that what you read in your local newspaper outside of Japan is quite different from what you read inside of Japan, and you can only appear as a fool.
Do not expose any tattoos that you might have. Tattoos are traditionally linked to the Japanese Mafia.
Respect food. Finish your plate. Don't walk around while eating.
Do not tip people - anywhere, ever.
If you need to make/receive a cellphone call, leave the room/restaurant/train compartment.
If you take a picture with your cellphone or compact digital camera, make sure that the "shutter sound" is switched on. People are afraid of secretly taken pictures, specially in public places.
Be very careful how you behave in general. People will politely ignore if you behave in a rude manner. This does not mean that it's ok. I have seen many people who started to become more and more rude simply because nobody told them off. It can breed a certain level of arrogance since people think whatever they do is ok.
Regarding some of the comments below
I would like to make a statement here regarding the accusation in the comments of me being sexist. I take any kind of discrimination very seriously and oppose them heavily. Therefore, I am even more upset when I am myself accused of being sexist. I considered this quite well and came to the conclusion that there is a need to comment on this. I perceive neither the comments nor my reply to be here in the right place, but as long as the accusation stands below, I am convinced that a proper reply from my side is absolutely necessary in respect of the weight of those accusations.
About the question about putting people in the same context as food:
"Women" in this topic are objects like Natto!
The accusation seems to be that a person asking me in direct sequence the questions if I like a type of food and if I like Japanese women is sexist. Me answering according to the question instead of rejecting the question as sexist, was making me sexist just as well. This means however that if someone said in one sentence to someone of the opposite sex: "I love this country, and I love you, too" would make someone sexist since it also compares a person with an object. I oppose this conclusion heavily. What introduction will one have to make then before talking about people to not degrade them and being accused of sexism?
About the question if the short time a tourist is in Japan matters:
Why is your taste important as a tourist about "Women" of a country?! Women are foods or you are going to buy them or get married with them in a short period of time? Surely these are not my questions as it is not important for me your or the others tourists' reason to travel to another country but this question is "sexist".
This question was asked by a Japanese person living in Japan to me, a foreigner living in Japan. While this page is not meant for expats, but for travelers, many people on this page return over and over to the same country and are therefore interested in the culture and mistakes one can make when having longer interactions with locals. My example does not address a weekend-tourist who only sees a few of the most famous temples in Kyoto. But regardless of this issue, nothing in this context is sexist just because the situation described does not apply to short-term tourists.
The context is about comparing a preference of a visual appearance of people in one part of the world to people of another part of the world. To perceive a visual difference between Caucasians and Japanese people is not sexist since it does not compare man to women in any way. It is further not racist since it is merely the observation of a very obvious fact, not a allegation of inherent superiority of one of them. Visual attraction (i.e. when seeing but not knowing a person) towards the other sex is a biological fact - and not sexism. Combining the visual attraction with a preference to the visual appearance, being the matter of a certain body type and possibly hair color is not sexism either. It does not treat women like objects and it does not judge men being superior to women. Otherwise the mere question "Do you think this person looks attractive?" was sexist too.
Funnily enough, I read an article on askmen.com about the top 10 Japanese etiquette mistakes.
Boiled down to bullet points, we have:
I did three years of Japanese in school, and the chopsticks in rice was definitely one we learned, as was the wearing of shoes in someone's house.
Mark's answer is excellent and covers all the big ones. From experience, just thought I'd add some other / my own social faux pas:
While some of these might seem ridiculous, I've been chastised for most of them, and many still give me full body cringes just to think about. Painful memories.
Two additional points.
Also if you ask for assistence from a stranger in a public place (such as a train station or store), always proceed your request with すみません (sumimasen). To do otherwse would be considered rude.
By default, sit in the back, not the front, of the taxi. However, this isn't so much a Japan-specific thing as an anywhere-other-than-Australia-New-Zealand-specific thing.
The most counter-intuitive etiquette advice I've received is to not thank staff. The Japanese Language & Usage question Is it proper to thank waitstaff, cashiers, etc. for their service? discusses this, and the general consensus is that it's ok either way. Dave M G's answer had a section on why you might choose not to thank staff:
My bonus cultural observation: The Japanese concept of service is that it's not about the people. The person working at a store or restaurant is becomes entirely a representative of that place while on duty, and they check their individual personality at the door. So for the customer, the staff does not merit personal interaction the way other people do.
To a non-Japanese mind, it seems a little harsh, as in other cultures, like mine, we tend to think about the person doing the job. I tend to sympathize with the guy doing the minimum wage job. However, in Japanese culture, it's not an attempt to be superior to the service staff, it's an acknowledgement that the service staff are also not necessarily personally invested in the job.
In some ways, there is a certain liberation in the concept, because the staff can also detach themselves from the job so as not to take issues personally.
As a side note, don't worry too much about etiquette. If you're normally a polite person, and remember not to wear your shoes or toilet slippers where you shouldn't then you'll probably do fine. I've spent a total of about 6 weeks in Japan from three trips, and I'm not aware of making any mistakes, although I had one minor near-miss.
I'm not Japanese but have a lot of Japanese friends. I think bow is the best way to show respect to people. If you go into a restaurant, the manager or waitresses will bow to you should bow back and that should be ok. And the thing that will frustrate/upset most Japanese restaurant owners is that you use chopsticks to pick up a sushi or dip the rice in soya sauce. Also, they don't except tips at all. If you think the service is good, just say thank you and smile and that should be ok.
Also, when eating Ramen, making sounds is also ok as that means it's really good. The cook will be pleased to hear that.