Agreed with Btf.
I did no specific prep and knew no more than the AFCO were able to tell me. I had been an Air Cadet but didn't attend UAS. I passed at my first attempt.
This is not a brag (although I realise it sounds like it). It's true that there is a fair amount of inate ability required. Engineering students with parents who are pilots are probably well prepared already!
Best of luck.
BV