For me.
Search the online database as thoroughly as you can in advance.
Apply for a temp. reader card online/by phone and order as many documents in advance as you can.
This will save you time when you get there and will get you familiar with the file syntax and their search engine which throws me from time to time.
If you are having difficulties pre-ordering online call them, I have found them very helpful in this matter.
I find it easier to photo pages rather that try to take copious notes so bring whatever it is that you use smart phone, camera etc and a charging cord. There are sockets at the reading room desks. If you must make notes follow the online instructions and take a pencil (no eraser)
Bring your proof of identity and on arrival go to the locker rooms to secure your bags or other items that you cannot take into the reading room (lockers are free) and go get a permanent readers card issued
I was last there in May and had to have my reader's card renewed the photo station had moved to near the entrance of the reading room.
Do pay attention to the instructions regarding use of document supports and handling in the reading room or you (gently in my experience) will get a telling off.
You will be limited by the number of files you can take from your assigned pre-order locker to the reading room at any one time. Keep the yellow ticket that comes with each order and return it with the file to the hand in desk when you are handing the file back. If you have a lot of documents to go through, and had pre-ordered your maximum number start ordering your next lots about 20 mins before you need them.
All in all I have never had any issues with the staff .
WO 32 are the files of the War Office and its successors. They will be subdivided classes such as that shown in this link
https://discovery.nationalarchives.g...ils/r/C2554586
John