The currency is the yen. Check the exchange rate . One or two shops even accept payment in US dollars. Major credit cards are widely accepted. The use of traveler's checks never caught on in Japan, but the biggest hotels and shops accept them.
Conventional checks are almost unheard of in everyday life.
No one tips, but a service charge is included in some bills. Browse around the travel counters in the Arrivals lobby at the airport and look for a mode of transport that suits your destination and budget. It takes the trains about an hour to reach central Tokyo. The buses don't take much longer - when the roads are empty. While you're waiting for your bus or train to leave, look around for a merchandise-bedecked kiosk or convenience store.