I start my background characters’ names with Z so that their names appear at the bottom of the list. Then I write G or B depending on their gender, so I don’t accidentally add a boy in a girls’ locker room scene, for example. Then I write a number starting from 1, so all my extras have different script names.
My extras’ names will end up something like:
Summary
ZB1
ZB2
ZB3
ZG1
ZG2
ZG3