When you put in your booking you can request a specific stateroom in the special request section. Tracey will do her best to accommodate you but it will be based on availability.
This ship has a lot of different areas with a lot of ammenities. I personlly don't think there is a bad place on the ship but you might like one area over another.
When in doubt book as mid-ship as possible and near to the elevators - that way you can get places quicker - especially the cupcake store