Based on my ongoing experience, here's a rough idea you can make in your own way :3
Study and master Hiragana and Katakana, there's plenty of online charts and games online like Adobe Flash to help you master them.
Even native Japanese children begin by studying and mastering the two.
Start off with about a handful of JLPT level Kanii, Vocabulary and Grammar, this will make it easy to understand some if not basic readin and listening.
Get use to listening to Japanese news, podcasts, YouTube channels and even anime.
I've been listening to Japanese media for years and I'm still struggling somewhat
Listen to Japanese songs and have lyrical Kana handy so you aren't guessing what is being said :3
Immerse yourself, involve yourself in the language everyday including culture too.
I'm sure others have different ways they began :3