Either buy a text book series such as Genki or use Tae Kim’s grammar guide: http://www.guidetojapanese.org/learn/grammar – working your way through the Basic, Essential, Special and Advanced sections.

RTK is a good option if you want to work on kanji, it isn’t required but some find it very helpful. It doesn’t have anything to do with grammar though, so you’ll still want to be doing textbook study at the same time.

I don’t like the whole mnemonics thing so I’m not going to be buying Remembering the Kanji, I’m just going to do all levels of JLPT with Read the Kanji instead. I’ll check out Gakuu but I think I’ll just look over Tae Kim’s grammar guide for a while first. Human Japanese might be worth checking out too.

Make friends on Lang-8, a few people on there are teaching me bits of Japanese, one person keeps giving me complex sentences then goes over each major grammar point, she also gives the English version to help break it down.

If he wants to continue learning in the structured way that Textfugu provides, then a textbook is ideal, whether it’s an online or offline one (both have different advantages). I’m not sure what you mean by incorporating writing, the best thing about good textbooks are the way the reading exercises are structured so as to build up in complexity as you progress, introducing new grammatical points into them. Genki has reading comprehension exercises right from the beginning, because they’re designed for the appropriate level of each chapter.

Reading short articles and stories in Japanese that’s geared specifically towards the reader’s level, right from the beginning, provides an excellent sense of progression and was more useful to me then trying to jump straight into and struggle with native material. Though people learn in a lot of different ways.

When I finished Textfugu I did RTK which I HIGHLY recommend and Tae Kim up to Special Expressions will help. I’m not really using a textbook (because they bore me) and instead working through A Dictionary of Basic Japanese Grammar… Also doing Core 2k Vocabulary since I recently finished RTK.

Whatever you do, make sure you IMMERSE yourself in Japanese or else your time spent studying will be for nothing.

Just ordered that book missing, thanks. Looks really good from reviews and looking at pictures of a few pages.

I’m reading Japanese for Busy People II just now and it’s quite good. It’s free from my Uni library though, and I’m pretty busy atm, so it suits me well haha.

Everyone’s made good suggestions so far, look here too: http://forum.koohii.com/viewtopic.php?pid=95122

Third on Japanese Sentence Patters for Effective Communication. Go though one or two patterns a day. Practice making your own sentences out of them. (Lang-8) I don’t think it gives very good explanations though or tons of examples but supplement it with dictionary of basic Japanese Grammar for a bit more clarity and in-depth info and KABLAM progress city.
I did RTK and found it helpful, some don’t. Never heard of this Kanji Damage…..maybe wirth looking into.

As far as textbooks, I agree with missing (again) for the most part, unless you are going through them with a tutor or instructor, they’re not worth it. You can get the same stuff online for free.

For vocab, I could not force myself through the core decks for anki. Too boring. I actually really like readthekanji.com (especially after RTK). It presents the vocab by grouping words with the same kanji so you really get a hang of the readings so you are learning kanji readings and vocab at once. It does cost money though….

Then there is reading, I suggest novels over manga because the usage is more common and you get full grammatically correct sentences. Don’t expect to go too fast though.