I think you can go situational ...
there are always good and bad days in a club ... days when no one is dancing and nobody seems to have fun and days when the club is exploding...
the are certain types of clubs ... packed ones where you literally have to walk over everyones feet to get to the bar and ones where you have space to break dance
different types of music .. you can ask if they play good music and you can tease them about they're taste in music ...
Are you leaving allready?Did you just get here? there are so many questions you can stack that you can talk about the club for half an hour.