There are many ways to improve your Japanese and fluency. One way is through a good textbook another is from speaking to people in Japanese. My Japanese teacher always told us that beer makes you speak better Japanese and I took her up on her word. I found that my spoken Japanese improved dramatically when I found a local Yakitori restaurant that became my local. I found that meeting Japanese people there and striking up a conversation greatly improved my fluency. Getting a Japanese girlfriend also has great benefits in improving your Japanese. If you prefer the textbook method I highly recommend the following Japanese Textbooks.
• Shin Nihongo no Kiso I & II – The Shin Nihongo no Kiso series is great for studying grammar and the stuff that you will find on the Japanese Proficiency Exam.
• Shin Nihongo no Kiso Japanese Kanji Workbook – This is great for learning and practicing all the kanji that you will find at all levels of the Japanese Proficiency Exam.
• A Course in Modern Japanese by The University of Nagoya Press
• An Introduction to Modern Japanese by Osamu Mizutani & Nobuko Mizutani
The above books were really helpful in improving my grammatical Japanese and my reading/writing. I also recommend the following dictionaries.
• Kanji & Kana a Handbook and Dictionary of the Japanese writing system
• Kankyusha`s Japanese-English Dictionary
I hope this helps and inspires you to improve your Japanese like it did mine.
The Secrets Of Speaking Japanese Fluently