Purchase an IC transport card
Pasmo and Suica are the two main IC transport cards used in Tokyo. These reloadable cards are convenient not just for travelling on trains and buses, but also for paying at selected stores and restaurants. You can get a card from train station kiosks and ticket machines for a refundable ¥500 deposit. Overseas visitors can even pick up special IC cards like the cute Sanrio-themed Pasmo Passport, which also gets you additional discounts on attractions in Tokyo.