Well, as dumb as this may sound - I started to learn Japanese many years ago through watching old Japanese Anime on VHS, of course this progressed to DVD e.t.c as time went on.
As my interest in learning the language grew, I decided to learn Katakana/Hiragana through the many tutorials online, starting with the basics.
I bought a large dictionary, and use it to refer to for things I don't recall.
Learning Romanji was fairly easy, although a lot of the time - the spelling is nothing like the phonetic pronounciation.
In short, Google "HIRAGANA KATAKANA TUTORIAL".
Advice, don't jump in with Kanji!