This file includes two crochet legging patterns. One is a more light and subtle, chic leg warmer, and the other is made to be bulkier for colder environments. Either can be made in multiple colors and sizes. I would suggest measuring the length of the calf around the widest part to get the size you need to make.
Any worsted-weight yarn will give you the correct gauge. So, check your gauge if you choose to use a smaller/heavier weight yarn or smaller/bigger hook.