there is a lot on youtube that you could check out!
if you're going in a group make sure you have at least a day to yourself to go off and explore
also don't say "sumimasen" too much, they only appreciate it to a point
when you go into a store, there will be abasket to put all your things in.. (don't forget)
also you don't give the money to them via your hands... you place it in a small tray that should be there..
if you go when it's raining, there will be like these bag things, that you put the umbrella into, so that you don't drip it into the store, and also the chance of having things stolen in japan are pretty low, so you can leave an umbrella in the holder out the front of the shop :)
DON'T jaywalk or anything like that, stick to the traffic laws even if there are no cars etc, it's just a really normal thing to do there
"gaijin" is the term for outsider.. it's generally used in a negative context, but don't feel too bad about it... my teacher explained to me that even though there might be a lot of forigners in japan, due to the population many japanese people can go through weeks/ days without seeing a forigner, so they may not be being mean... just ignore it
uhmm my friend and i had some weird experiences with old men being creepy... so watch out for that haha
the drinking age is 20 or 21?
you can be kept (by the police) for 24hrs without having a free call... so don't mess up or your family/friends could get very worried! (i think this is the time i can't rember perfectly)
there are fireworks for sale.. but you generally can't use them so be wary..
some japanese people will try and practise their english on you, so be patient... and on the other half to this many japanese people who may know english will ignore you as to not embarass themself by having bad english... don't feel bad if you get ignored :s
hope your trip is awesome!! ^^