- Avoid eating at convenience stores as much as possible. The food is good, but you can get similarly priced food that is much better at any restaurant you might walk into.
- Bring cash. Credit cards only became a thing about 6 years ago.
- Police officers have very little to do, so if you're lost, use them for directions.
Kiji Some of the best Okonomiyaki in Japan.
Tsurutontan (multiple spots) The most stylish, delicious, bang-for-your-buck Udon in Japan. If you're feeling really hungry, ask them to double your portion or 1.5 it, because it's free. (Japanese: Double-portion == Nitama, One and Half portion == Ittengotama)
T's TanTan Best vegetarian ramen in Tokyo
Mister Donut If you do not have Mister Donut in your country, do yourself a favor and head over to one. Pick up a glazed Pon de Ring. My most favorite dessert in the world.
Super Potato Prepare for video game nostaglia! An emporium of all things 80s and 90s video game.
Tskumo Robot Kingdom This is where all of the best Japanese robot wrestling champions buy their robot wrestling parts. It's on the second floor of a Tsukumo, which is a general computer parts establishment. The building has two second floors, but the one with robots has signs pointing to it. If you get lost, Japanese people understand the word "Roboto," so you can ask for directions if you're having trouble. Also, don't be afriad to say "Domo arigatou mista roboto."
Maid Cafe: Maidremin If you must go to a maid cafe (be prepared to feel awkward for an hour or two), go to this one. Tips: Pay extra for the dance. Pay extra for a photo (no free photos allowed). Pay extra for unlimited alcohol. Observe Otaku Japanese in their natural habitat.
Gatchapon Hall It's a store filled with little those little plastic ball vending machines. These make great gifts to bring to people back home, as the packaging and items themselves are so very Japanese.
Aki-Oka Artisan An awesome little artisan street hidden away underneath the Yamanote line. I recommend stopping by here after a romp around Akihabara to see some cool artisan craft. Things like an all-wood store or extremely accurate metal castings store. Less mainstream feel than Harajuku and Omotesando (though Harajuku and Omotesando are both cool).
Harukoma(春駒 はるこま) for the best sushi in Japan. Seriously. Simply the best.
Omoni (Near Running Man|Near Grand Front) for my favorite Korean/Japanese Okonomiyaki fusion. Delicious.
Tsurutontan (multiple spots) for the most stylish, delicious, largest Udon in Japan.