When we mention about sightseeing in Tokyo, we normally think of the busy and never-sleeping Shinjuku district, the young and energetic Shibuya and Ikebukuro districts, the electronics hub in Akihabara, the traditional-meets-modern ambience of Asakusa district, and the streets of Ginza district lined with boutique labels.
These are definitely popular tourist spots in Tokyo, and I personally would also recommend them to first time visitors to Tokyo - each district has a distinctly different atmosphere to it, but yet share a common metropolitan Tokyo essence in them. You can't go wrong with visiting these popular spots, and they will definitely give you a wonderful Tokyo experience.
Being based in Japan for an extended period of time has given me the opportunities to explore the smaller suburbs of Tokyo, which are mainly used for residential purposes. I do like walking through these areas as more often than not, I would chance upon a good cozy restaurant which serves pretty darn good food with a nice selection of Japanese sake. These shops, however, lack the publicity of the more modern restaurants or large chain restaurant franchises as they are owned and run by a just handful of people - usually family members or old couples. What I find common with most of these family-run restaurants is that they take pride in their menu, and will serve delicious food at much more affordable prices due to the lower overhead costs in these areas.
The image in this post is taken around Keisei-Tateishi station, located in Katsushika Ward of Tokyo. If your itinerary allows for it, I would highly recommend taking some time off and exploring the suburbs of Tokyo - you may find a gem there!