My coworker told me to exchange money (US dollar to Yen) at the Narita Airport and I did. The rate is much better than exchanging the money in USA.

I also rented a cell phone at the airport. Although I only know one person in Japan, but having a phone make me feel more secure. You can dial international call but the instruction is kind of... long -ui-

yep, Narita is the best place.

Also, if you plan ahead and take traveler's checks, you get an even better rate, for some reason.