So, if you don't have time for planning or if you visit the city just for a little while, I would recommend you a sightseeing tour operator. In Tokyo, Hato Bus are offering two interesting tours, one for the morning (Tokyo Tower, the Imperial Palace and Asakusa) and one for the afternoon (World Trade Center Building observatory, and a boat ride on the Sumida River to Asakusa). Interesting, well selected places. Plus, you may have the chance to use a kawaii bus... like this one, decorated with Hello Kitty, photographed a couple of weeks ago in front of the Tokyo Station.
EXIF info:
Nikon D90
Lens: 8-16mm F/4.5-5.6G
Focal Length: 16mm
Aperture: F/5.6
Shutter Speed: 1/1200s
ISO Sensitivity: ISO 200