You can easily spend a whole night in Tokyo, just make sure you find somewhere you want to stay for a good portion of the evening. I should mention that the Yamanote and other such train lines will shut down at around 12:00-12:30am, so unless you're gonna take a cab to get somewhere, you're gonna be in that area until about 5am or so when the trains are up and running again. If you're looking for clubs and party places, Shibuya or Shinjuku are your best bet. If you're looking for other things, then let us know and I'm sure we can point you int he right direction.
