shooraijin wrote:Wow, congratulations! I hope the stress gives way to real blessings. Perhaps some of our folks like Kaori or bobtheduck have some advice for you.
いやぁぁぁぁ、I don't know that I can say anything other than general and obvious things, for example, learn as much of the language and culture as you can. Not a single moment that you spend on language/culture study will be wasted, and if you make an effort to undersand the way that Japanese people think and act, e.g. the indirect communication style, that will help you out a lot. Indirect communication in particular is something a lot of non-Japanese people really don't get, but Japanese people often don't express their preferences directly, so you have to watch for subtle clues. For example, if you ask someone to do something and they say "That would be difficult" it means they probably don't want to do it. And on the other hand, if they say something like, "Would it be possible to go to _____?" that means they want to go there.
Although I'm not sure whether it is good to say this kind of complaint, I have to also mention that recently I have found that information about Japanese culture that I read in English (on the internet) is just not very good. For example, whenever in my internet wanderings I stumble across a Japan Times article and read it, I feel like the Japan Times ought to be called the "I don't understand Japan" Times.
So できるだけ read things in Japanese if you can.
I don't know where your Japanese level is, but what I have read so far of the book 日本人の心がわかる日本語 is really excellent and has definitely deepened my understanding of Japanese culture (this after having lived there for six years). It's meant for Japanese-language learners, so it's at a nice upper-intermediate level and has furigana and glossaries to help you. But it is entirely in Japanese other than the glossaries. If that's too difficult, there's also a 日本人の心 that is a bilingual book so that you can read in English and still see what the names for the concepts are in Japanese (e.g. 和). I read that a long time ago and remember thinking it seemed vague, but it is at least a Japanese perspective, and I think if I were to reread it now I would understand better the things that are being referred to (having experienced them more).
As far as figuring out when to use polite form and when to use plain form, you can generally follow the lead of the person you are talking with, but if you are talking to someone who is significantly older you should probably use polite form even if they are using plain form. I guess another thing that will help prevent misunderstandings is if you have a sense of the way that polite form is polite but also can be distancing (use it with someone who wants to be your friend and it will come across as "I don't want to be your friend") and plain form can create a sense of closeness. So if someone is using plain form with you that doesn't necessarily mean they are being rude, it actually is something that, if mutual, creates a comfortable, warm feeling that feels really good to Japanese people.
If people ask your age a lot, it's because it's an Asian thing and they are trying to figure out how they are expected to act towards you based on whether you are older or younger than they are.
You might already know this, but it's good to know the nuances of the different ways of saying "yes." はい doesn't necessarily mean "I agree," it often only means "I'm listening" (verbal feedback to show you are paying attention). ええ is more clearly "yes," うん is an informal "yes" you can use with friends, if you want to clearly convey "I understand" you can say わかりました (informally わかった)、 and if you really want to say "yes" in the sense of "Yes, I will do what you are asking me to do," you can say 了解（りょうかい）です (fairly formal, e.g. for work situations).
Also something you might already know, but don't add ～さん to your own name when introducing yourself (a mistake I have sometimes seen people do; as far as mistakes go it is a pretty bad faux pas). And generally you should make sure to always add honorifics to the names of people you are talking with unless they specifically tell you not to or you are on very close terms and feel pretty confident it is okay.
Generally speaking, the more you try to adapt to a Japanese way of life, the easier things will be for you while living in Japan, i.e. if you try to eat a lot of Japanese foods rather than going to an expensive imported foods grocery store (the one in the Sunshine City mall, for example) and paying ridiculous prices for food because you want to eat something that Japanese grocery stores don't carry.
Since you're in Tokyo, prepaid rail cards (Suica, Pasmo, JR Pass) are convenient and nice to have. You will probably want to get one, though there's no rush since you can always pay for each trip separately.
．．．思ったよりありましたね。 Anyways, I will stop talking now and just say congrats, have a safe trip, and I hope you enjoy Japan!