Tokyo never ceases to amaze me by its contrasts. It is a very impersonal city, yet its people remain extremely hospitable. It is one full of vending machines chocked full of about everything that strikes one's fancy, yet maintains an unerring sense of service. It is one where toilet papers are sold in public restrooms, yet tissue papers are passed out for free in front of train stations. It is very crowded, yet it respects personal space. Even at the subway station during rush hour, often passengers would wait for their trains in orderly lines. Riders immediately turn off their cell phones when boarding public transportation, and the bus P/A system often reminds passengers that cell phones bother their neighbors. Often, visitors to Japan often have very little time for Tokyo, preferring to bypass it for the more historic Kyoto. Personlly, it is an enjoyable city, not as expensive as one would think.
Highlights include 1) people watching during cherry blossom season; 2) shopping at the world's largest department stores; and 3) discovering the neighborhoods.
Quick Tips:
Others have said this before, but I have to reiterate. Visit Japan during the spring cherry blossom season if you could, although this is extremely difficult to plan, as this season sometimes lasts only a week. Otherwise, go during the fall, when the maple leaves turn a majestic red. If possible, try to fly into Tokyo and out of Osaka, or vice versa. This way, you can cover more of Japan without having to double back).
Best Way To Get Around:
Needless to say that Japan, and in particular Tokyo, has an excellent train/subway system. Once in the city, this should be your only mode of transportation, though splurging once in a while on a cab when you are totally exhausted is doable. The map of the subway is really a soba noodle maze, but once you get used to it, it's a cinch. We found that we also spent most of the time on a couple of line, the red and the grey, which cover most of the usual tourist spots, so learning to know them is not too difficult.