Useful resources for learning Japanese
There are many different techniques for learning a language. Some people prefer textbooks, some people prefer only digital material. Some learn best by hand writing everything many times, while others can read and retain that information just as effectively. Currently, students are bombarded with a massive variety of study options, in particular apps (Apple or Android) and web-based interactive sites. I think they can be very useful as long as you realise you must practise hand-writing as often as possible.
If you are a student learning Japanese for the first time, the following textbooks are useful in helping you progress.
I suggest you supplement them with apps (Android or Apple) for regular practise, as regular little chunks of studying helps enormously.
Obentoo Deluxe
Beginner
This series has been used in schools in Australia for many years. It is quite good at explaining and drilling patterns and has plenty of exercises for checking your understanding.
Be aware that they only use the "masu" and "desu" form, which is polite language.
In my experience, this book was used for students in their first year of learning Japanese.
Obentoo Supreme
Intermediate
Obviously a continuation of the Obentoo series (2nd level). In my experience, this book was used for students in their 2nd and 3rd year of studying Japanese.
Again, it is quite good at introducing new language and offers a variety of material.
The following series are world renowned. I have used them myself and can vouch for their effectiveness. There are two books to buy per level - a textbook and a workbook.
You can purchase a KANA version (activities are in hiragana, katakana or limited kanji) - I recommend this!
Or, you can purchase a ROMANIZED version (activities are in romaji) - ideal for the learner mainly interested in speaking.
Japanese For Busy People series
Beginner to Advanced
This series is "the most popular Japanese language textbook series in the world".
I recommend this series for mature learners and those wishing to challenge themselves a little more. The language of their examples is quite different to the examples I gave above. This covers a broader range of contexts and uses... more realistic or, dare I say it, more useful language.
There are three levels and, just like the Obentoo series, there is a "textbook" and an accompanying "workbook" per level.
In addition, the JBP series has a supporting app in the iTunes store.