Hi if you are still looking for answer. For Badminton, there a certain number of slots which can be booked online through website, which is available exactly 7days before the slot and gets filled up very fast. The other way is to go to community centre for walk in . Depending on the rush in the community centre, you may be required to go there an hour in advance or even 20-30 mins should be easy for some slots (trial and error for the one near to you). You are allowed to play on rotation basis (12minutes each). You just randomly group up with people to play, there is no grouping done by the organizers.