I've been experimenting with knitting hats the last couple of weeks. The first one was too large because I used a rather stretchy yarn. The second one was a bit small, but wearable and I really liked the yarn--Tahki's Bunny Print. The third one, using Licorice and black worsted came out just right. The pattern called for knitting them from the top center down, starting on double-pointed needles and then moving to circular needles. I began on straight needles and then just sewed together the small gap. This was much easier than dealing with a few stitches each on double-pointed needles. Part of the sizing problem is that the hat is sort of scrunched together on the needles so it's difficult to really tell how large it is.
Here's a picture of the three hats. The Bunny Print is the one on the right. I made the black and white one for my son's girlfriend.