In fact, when I got in one club a very cute german girl tried to talk to me on the dancefloor. But I didn't speak any German and she got angry, shouting "aaauuggh!! tourists!!!"
Also, for the clubs that forbid alcohol (hard drugs only!), they will refuse you if you are caught drinking in line or are visibly drunk.
Also, I was told to keep my mouth shut as they will sometimes refuse you if you speak English
At least this is how it was about 13 years ago. My friend was a self-described and un-ironic "hipster", who kept his finger on the pulse of the local underground, and of course he lived in Kreuzberg