Next time you're traveling or just chattin' in Japanese with your friends, drop the textbook formality and bust out with expressions they never teach you in school, including:
-Cool slang
-Funny insults
-Explicit terms
-Raw swear words
Dirty Japanese teaches the casual expressions heard every day on the streets from Tokyo to Kyoto from "What's up?" (Ossu?) to "I'm smashed," (Beron beron ni nattekita.)