Okay, with 84 sts to start, you can k5, k2tog, k5, k2tog doing this all the way around. Then knit a round plain and on the next, k4, k2tog, all the way around. Another knit round then k3, k2tog around the hat on the next one. Knit 1 round and on the next k2, k2tog around. Knit 1 round and then you'll do k1, k2tog. You can knit the next round or go right to the next dec round which will be k2tog, k2tog all around. At this point you'll have about 12 sts on the needles and you can cut the yarn leaving a tail, and thread it through those 12 sts like a drawstring and you're done. I usually thread the tail in a 2nd time too, just to make sure the top is nice and snug.