[SSJup81]

It's good to learn the alphabet. You should start with learning your Hiragana and Katakana charts, imo. Start with Hiragana, after you got that down, then learn your Katakana or vice-versa. After that, then it'll probably be wise to start learning the basic grammar rules. You can pretty much pick up books on that.

Of course, the best way to learn any language (if not able to go to the country and learn there right away) is to take formal classes.