The truth of the matter is that anything less than immersion won't work.
Listen to Japanese radio
Use Rosetta
Go through the Japanese for Busy People books
Listen to the Pimsler recordings
http://www.pimsler.org/
Eat at Japanese run restaurants
Go to Japan
Practice Aikido, Karate or Judo
Read some manga or buy some j-pop
Do a language exchange at your local library
And always remember that if your not immersed or studying hard you'll forget faster than you learned.