antzx6r
Keeping your eyes outside the aircraft as you approach the circuit is essential - as you say a notepad and pen is fine in navs but no good in the circuit.
What I do is to break aircraft in to different groups - where they are (circuit/departing/arriving) and where they are likely to be conflict. It is something that you develop with practice.
One way of helping developing the skills is to listen to aerodrome radio traffic on the ground - using an air band radio or scanner. Pick an arriving aircraft and relate the other traffic to it as it arrives. Even better be doing something else at the same time.