This here pro's perspective of the 10 most important attributes of a PA while doing location work.
Knows all the good cafes in the area (for food and coffee)
Is PUNCTUAL - God help you if you're late
Thinks ahead and sets up accordingly, eg: no power leads across the path of the models in an outdoor fashion shoot.
Doesn't talk $hit ie: banalaties / mindless small talk like a blithering idiot non stop.
Has a good sense of dress and dresses appropriately for the job. ie: No flip flops/sandals, baggy camo shorts or t-shirt to a black tie affair - Only the pro is allowed that right
Can coordinate the other crew (makeup, hair, dressers, etc) as required
Can lug vast amounts of gear
Doesn't mind working all the hours of day and night, eg: arriving on location at 2.30am to prepare for a dawn shoot.
Has a clean driving license and can drive any vehicle up to 5 tons GMV.
Can put up with the photographers difficult behaviour.