My older cousin is moving to Japan for a teaching job, and he asked me where I was stationed. I decided to give him some unsolicited advice.
I was on the island of Okinawa, south of the main island. It was fun but its way different from the rest of Japan. I got used to being taller than most men there, but somehow their fashions and pop culture are freakish clones of whatever was 15-20 years ago. Its weird.
Shop the 100yen stores, enjoy the food, don't forget to see the tourist destinations. Nothing is more lame than living in a cool foreign country and not seeing the sights. No excuses! Oh, 100 yen is about $1, so don't feel all rich with a 1,000 note in your pocket.
We were reminded pretty often that if you're arrested, make sure someone you know is aware. Otherwise you don't get food or blankets in jail. Also, if you drive, remember just by being a driver you assume a certain percent of responsibiltiy in an accident, even if it is shown to not be your fault. Don't run over Japanese kids, nobody likes an international incident on their record :D
Hi(sharply) means yes, short for Ohio Gozaimas. But if you say hi, they might understand you mean hello. Mizu is water, miso is a paste. I think... Domo between friends, Domo Arigato to the waiter, Domo Arigato Gozaimas to your boss or your girlfriend's dad ;). Tipping is considered rude. If you're not sure how to say something on the menu, just point to the picture and kinda grunt. They all think(know) we're stupid anyway, so its okay.
I don't recommend Orion beer. Don't marry a local, or a philipino. Especially if neither of you speak the other's language. Especially one you meet at a bar, ever.
Have fun. Take lots of pictures.