you must absolutty visit kurfursten street to visit kaisr-wilhelm-gedachtnis-kirche.
you must absolutty visit alexander platz to visit karl marx statue , television tower and nikolai-viertel.
Berlin is wellknown for its nightlife, so you definately have to visit one of the nightclubs when you are there !
Dress Code: From what I've managed to see - seems a busy and really fun one! People become more dressed-up in the evening, clubs begin inviting with all kind of actions, sounds, tricks and all they can.