Hahaha well as a 17yr old from HK, I'd have to say there's a lot of hanging out, every friday, saturday... people even tend to go out right afterschool.... you end up either wandering, eating, hanging out in cinemas or beaches <-- most popular. Although a huge number like to karaoke too, but thats slightly pricier, so only for special occasions.
Uhh... I know a load of teens that go partying every weekend too, even though they're underage. Don't join in, and thats normal everywhere... half the teens join in the parties, half don't.. everyone still gets along!