I was based very close to Osaka which is the 2nd or 3rd biggest city next to Tokyo, so there is lots to do, and I spent time in nearby Kyoto where there are a lot of national heritage sites, old shrines and temples. I went travelling in the winter vacation and went to Hiroshima, Hakata, Beppu, Osaka, Tokyo, Kamakura and Kyoto.
Useful local words: ‘irasshaimase’ ( the shop greeting, but for weeks I didn't know what it meant), ‘Ookini’ ('thank you' using the strong Osaka dialect), ‘sumimasen’ (‘excuse me’, but a very versatile word that can be used to thank, pardon yourself or apologise).
What not to pack: All the clothes I brought. I should have just bought them there.
What to pack: A small suitcase, for quick trips.
Couldn't have done without: My mp3 player and my laptop.
Word of advice: Do as many things as you can, and go alone if you have to. It is so easy to go with friends and be dependent on them, or make new friends and just stick with them. I met the best people when I went travelling alone, and those times were also the most fun I had too. Don't be afraid to just talk to people and stay away from tourist traps and other English speaking people.
NS, Japanese and Linguistics, Newcastle University