Side to side American girl doll skirt/18" doll by ConsultingM

Side to side American girl doll skirt/18" doll

Crochet
February 2011
Worsted (9 wpi) ?
5.5 mm (I)
doll sized
English
This pattern is available for free.

I need assistance figuring out how one tests gauge in crochet. If someone can tell me, that would be lovely! ^_^