The nightlife scene in Berlin is constantly changing. Most of what''s happening is in former East Berlin, so that''s a good place to start. There is ALWAYS something going on, but if you want to find the place to be, you''re going to have to ask around. Clubs where a famous DJ played last week are not necessarily good this week. Check out the periodicals "Zitty" and "Tipp" for a listing of what''s happening (available at any bookstore or news agency), and then ASK. Whatever you''re looking for: live jazz, good trance, gay and lesbian (best periodical to look for is called "Siegessaeule", a monthly), even swingers clubs and live sex on stage, you can find it, but don''t go just by the book.
Popular/famous venues: the KitKatKlub is an extremely famous club, whether from the musical Cabaret or its contemporary shenanigans. If shenanigans are what you''re looking for, the KitKatKlub is where you will find them. "Darkrooms" in the back (don''t even ask), gay and straight and anything else you might think of. I haven''t actually been to this one, but I''ve been told just-spectactors are not so cool with the crowd, so know that before you go.
Casino is right next to Ostgut, which just closed down, I think. Casino has been/is? home to DJs like Paul van Dyk and can be quite good, but catch it on a bad night and it''s not worth the entry fee. Mostly straight crowd. Right next to the Ostbahnhof.