Hi JustMe,
I'm self taught, i'm no where near fluent but I have been slowly learning for a few months now.
Yesterday, even though the first few chapters are a bit beyond my level, I started working on the 'genki' textbook.
It is very useful and gives you lots of background information.
To remember the characters (hiragana and katakana) to begin with I made flashcards. You can do a hiragana/katakana drill online where you do virtual flashcards, but i actually wrote every single one out *feels stupid* but in a way that did help because I took them everywhere and on car journeys etc I could practice.
For Kanji, don't start that until you know the hiragana and katakana because you will need to know the kanji readings, for example this kanji: 今, you may remember the romaji of it being 'ima' but you need to know it in the hiragana aswell, and so, you should learn the letters and sounds as soon as possible.
When you do get to more advanced kanji, I always find it helps to see if it looks like the meaning, for example the kanji for 'forest' to me, looks like a few trees in a forest. Some kanji you just learn because people around you use them a lot and you eventually pick them up.
Don't be afraid to practice your japanese at every opportunity, even if your just saying a few simple phrases. If you practice people can correct you and you get better through the experience.
Any questions please PM me, I have a bunch of japanese practice sites etc under my favourites if you want any.
Sorry for the long post!