All of my patterns are for the average adult size woman's head. If you need a size small, go down 1 or 2 hook sizes. If you need a size large, go up a hook size or 2.
Also, If you are a tight crocheter, go up a hook size.
I have crocheted almost my whole life. Over the years I have crocheted, painted, sewn, and many other things. For now, I am wrapped up in crochet and sewing!