This is how I do it:
Learn ひらがな(hiragana)、カタカナ(katakana) (AJATT blog says to do this after kanji, but I needed it for motivation)
Now learn ALL kanji in Heisigs book, "remembering the kanji". The easiest way to do this is to use the site:
Remember and review kanji flashcards online with James Heisig's "Remembering the Kanji" . You might find buying the book helpful (for stroke order and such), you can find a free sample somewhere (forgot where), or you can "aquire" the full book from elsewhere if you want. Try to do this step as quick as you can, don't learn anything else, just concentrate on getting it done, since after you're finished it makes everything a lot easier and faster. Also don't worry about the readings of the kanji, you can learn them later from context, which is much more fun.
Now at this point you will know ひらがな(hiragana)、カタカナ(katakana) and 漢字（かんじ）(kanji). Know you need some grammer.
Using an
SRS like
anki get your favourite grammer book/resource and add sentences of the grammer points. I used
Tae Kim's Japanese guide to Japanese grammar (Which is nice and free =D)
If you don't know what to put on your cards heres a basic template on how I would do it:
Question Side:
アリスは食べる。
Answer Side：
食べる ＝ た・べる ＝ To eat
When I do my daily reviews I write out the sentence and say the sentence aloud.
After adding sentences from all the sections of that guide, I had a good enough grasp of the grammer to be able to get sentences from manga, games, blogs, whatever. (I'm playing Final Fantasy 7 in Japanese at the moment) Just look up the words you don't know, understand the sentence and add the sentence to you SRS. If you still can't understand when you've looked up the words, then skip it, eventually you'll be able to understand it.
When putting in your sentences, don't translate them. You want Japanese to be Japanese and English to be English.
Also try to have something Japanese playing in the background all the time. Be it anime, doramas, Tv, radio, whatever. This will help your listening, and your pronunctiation. You can download japanese shows with bittorrent, share, winny, perfect dark, or you can stream live japanese tv with a program called KeyholeTv. Just play them in the background.
I'm not very good at explaining, most of it you just figure out as you go along.
If you have any questions about AJATT,
kanji.koohii.com forums are very useful.