You should already have basic crochet skills, ie. single crochet, half double crochet, double crochet. You will also need to know how to make a magic ring to start the hat, which is SUPER easy. If you don't know how to make one, just check YouTube, that's where I learned :) Type it in their search bar and you'll get a ton of videos.
Sizing / Finished Measurements:
Sizes range from newborn to adult.
Size G crochet hook for newborn. Size H crochet hook for 6 months to adult. Size 3 yarn, I like Bernat Softee Baby.