Definitely check out the FAQ section. Below are just two important answers.
What should I do if I need help or get lost?
In Japan, the equivalent of "911" is "119" - calling that number from any phone will connect you to fire and emergency medical services. To call the police, there is a separate number: 110. Another useful tip is kōban, or "police boxes" - these are small neighborhood police stations found all over Japan. It's very common in Japan to stop at a kōban to ask for directions. Finally, here is information on contacting the U.S. Embassy in Tokyo.
How can people call me while I'm in Japan?
To call Japan from the U.S., dial: 011 81, followed by the area code and phone number. For Japanese cell phones, the area code is 80 or 90. One of the easiest and cheapest ways to call Japan is through a VoIP service such as Skype.
JNTO maintains 14 offices in key cities around the world, through which a wide range of tourism-related promotions are carried out. Each overseas office is responsible for promoting travel and tourism to Japan; one of the most important functions is to help the travel industry encourage their clients to visit Japan. You'll want to spend some time on this site to gather information for your trip.
Great tips and information may be found on this website - below are just two important tips - you'll want to review all of them!
Before You Go - The voltage in Japan is 100 Volt, which is different from North America (120V). Japanese power outlets are identical to ungrounded (2-pin) North American outlets. While most Japanese outlets these days are polarized (one slot is slightly wider than the other), it is possible to encounter non-polarized outlets in some places. Some North American equipment will work fine in Japan without an adapter and vice versa, however, certain equipment, especially equipment involving heating (e.g. hair dryers), may not work properly or even get damaged.
Learn - Correct manners are very important among the Japanese. Also as a foreigner in Japan you should be familiar with at least the most basic rules.