Be sure to get the JR Pass if you plan on going to multiple cities.
Moniez: either bring cash or bring a debit card
- I bank with SF Fire Credit Union that rebates ATM fees and has no foreign currency exchange fees. Other credit unions may have similar benefits.
- You typically want to bring cash around to pay for things. Unless you’re dining at a fancy restaurant or shopping at the department store, I typically err on the side of using cash, as you may not always be able to use your credit card. Little delicious mom and pop ramen shops may not take your card.
- My friend Rob opened a Charles Schwab Investor Checking account on the internet, and their debit card was good at probably 95% of the places we went in Tokyo and Kyoto. They refund ATM fees and don’t charge for foreign transactions, too.
- His additional tip:
You don’t have to go to a Charles Cook or other currency exchange in America to get Japanese cash for your trip. I went to my regular bank and asked a teller to order me a few hundred dollars in yen to take on the plane. I had to wait a few days for the order to arrive, but the exchange rate was the market rate instead of the terrible rate you’d get at Charles Cook or worse, at the airport.
- If you plan on going between Tokyo to Kyoto/Osaka, it’ll pay for itself, and it’ll include the price of riding the Bullet Train 🚅.
The JR Pass is nice for getting from city to city - you can also use it on the JR Yamanote Line subway that goes in a circle around a lot of the fun tourist wards in Tokyo, and you can even use it to get to and from Narita Airport on the Narita Express high-speed train. If you want to give yourself a nice touch of luxury on your trip, but can’t afford to fly business class, consider upgrading your JR Pass to the Green pass, which lets you reserve seats on the Green Car. It definitely costs more than just buying a round-trip ordinary car ticket on the shinkansen, but the Green Car has nicer seats, more legroom, and is quieter. It’s just pleasant. 
You don’t need to pay extra to order one online before you leave, but get a Pasmo or Suica card (or in Kyoto, an Icoca card) as soon as you see a subway ticket machine that sells them. You can use it like a Clipper on the subway, use it on the bus, even use it to buy food at a convenience store, and you won’t have to spend as much time fumbling with coins or trying to figure out exact subway fares. Once every day or two you just find a recharge station and dump your spare coins and maybe a ¥1,000 bill onto your IC card and then you’re back to zipping around town. 
- I’m currently using T-mobile’s ONE Plan in the US, which gives me free data roaming in Japan at 3G. If you prefer something more reliable and want to use this option, I suggest upgrading to their One Plus Plan.
- Another option is to get a local SIM card at the airport.
- And yet another option is to get a mobile hot-spot from the airport:
$8 a day with unlimited 3G data and a spare battery. It was waiting for us to pick up at the airport, and came with a postage-paid envelope, so when we got back to the airport we just put it in the envelope and put it in a mailbox. For 1 person a SIM might be better, but for a group of people sharing data, a mobile hotspot was perfect. Google Maps or Gurunavi really makes planning a subway trip easier. 
Don’t be afraid of the language barrier! Tokyo and Kyoto are very English-friendly, with most signs and public announcements in English and Japanese. You can really get away with just learning some phrases to be polite, like learning how to say hello for the times of day, good bye, please, thank you, excuse me, how much is this, and I’m sorry. More is always better, of course - people will be surprised if you say “gochisousama deshita” after you pay for your food.
Traditionally, the Japanese have associated tattoos with the Yakuza (the Japanese mafia). Because of this, if you had body art done, you would likely not be welcome in a pool or spa, as they want to be extra cautious of the possibility that you could be a gang member. More recently, you’ll likely have less trouble, especially as a foreigner. And I’ve heard word that this is just generally more relaxed now.
Another great tip from Rob:
A coin purse is not a very common accessory in America, but in Japan the $1 and $5 equivalent are coins, so you quickly amass a lot of change in your pockets. Plus they don’t seem to share our obsession with pricing things at $x.99, so lots of purchases will turn out to be 340 yen or 958 yen and you’ll wind up with tons of coins, especially since so many places seem to want cash. A coin purse will keep all your change in one place and makes a good souvenir after the trip.
Something that’s notable to me about TV in Japan is that there sure is a lot of time spent on people eating food. You’ll often flip through the channels and bump into footage of screeching girls yelling “Oishiiii!!!” or guys belching out “Umai!!!” It all means: DELICIOUS or YUM. Moreover, if you end up seeing a Variety TV Show, you’ll actually be watching a panel of people watching people eat. YUM.
When my friends and I were poor starving students, it was rather painful to be watching people eating delicious food when we were eating cheap ramen or soba from Family Mart.
Japan has an incredible lost and found system in place. If you lose something on a train or in a taxi, check with the local police. You may just get your lost item un-lost.
Liam Akin, a good friend that I went to school with in Kyoto, went on to live several more years there and documented some of his observations about Japanese culture while he was there in his web comic: Fried Sushi. He’s an amazing artist, and he is always able to bring a smile to my face with his humor.
 Huge thanks to Rob Tibbetts for his additions and thoughts! Tons of great information.