When do bookings show up on BookMyShow for upcoming movies at a particular cinema? 

We too wait for the new releases just like you. To be honest, cinemas open bookings 2-3 days prior to the release date and this can vary from cinema to cinema. 

Once bookings go live by the cinema, you can grab your desired tickets and enjoy the show. 

In case you still don't see your desired movie in the cinema near to you, chances are, that the cinema is yet to go live with the desired movie. 

Why don't you hit the interested tab under the movie section on the app? You will receive a notification once the bookings are live.