One rec. on your first day here- I recommend a food tour. Especially those done by my friend Anne, at www.arigatojapan.co.jp -- the reason why? They teach ordering, etiquette and give you confidence to explore more food during the rest of your trip.
The ALL STAR TOUR, or the ASAKUSA TOUR are both awesome options. If you are headed to Kyoto or Osaka after Tokyo they also have tours there. <3