[mira]

You should learn Hiragana, Katakana some Kanji and speak some before you go. Hiragana and Katakana are the easiest, each have about 46 characters with things called smalls.

Hiragana is important because it is the Japanese alphabet and any Japanese thing can be written in it. It is used for words that don't have Kanji and for something called Furigana which is in Hiragana but is written in small letters above Kanji to show how to say it. It's also used for particles.
Example: つづきから

Katakana is the other alphabet and is used to write foreign words, onomatopoeia, or to make something look fancy. It has a lot of uses, you will just have to pick up on it.
Example: メロディ

Kanji is characters borrowed from Chinese and Japanese have a few of their own too. There are about 2,000 Kanji that Japanese learn and each have an "on" reading and a "kun" reading. The "on" if from Chinese and written in Katakana and the "kun" is Japanese and is written in Hiragana. Each Kanji have different meanings and multiple readings.
Example: 銀色

Learning Hiragana alone will not be enough if you want to read thins in Japan. You should learn at least Hiragana and Katakana and learn how to write and pronounce each. Kanji is really important but it is hard. You should at least try to learn some because it will really help.