The thing about learning Japanese is really just memorization, IMHO. If you know Chinese you can (kind of) breeze through the kanji, since you only need to know the pronunciations.

The hiragana and katakana are pure memorization though. (-__-) There's no good way around it, as far as I know.

The grammar is all about application. If you write like, a little diary in JP or something, then it'll get better. And when you've learned something new, try to use it. It's easier to remember that way.

And one last thing. If you want to pick up on vocabulary, find a JP song. Get the lyrics. Try to find out what every word means, and try to pull out your own translation. If you like the song, not only is it fun, but educational in the long run too!!