The body of the hat is 20-30 rounds. I've knit a few plain hats but they are boring to knit so I'll try different ideas. A round or two of purl stitches in a different color, a round or two of purl stitches in the same yarn, a stitch pattern that can be easily divisible into the stitches (4 stitch patterns work well). I often use stitch patterns I've used for socks I've knit (see another of my blogs, Knitting Only Socks). Simple Fair Isle patterns just above the ribbing would also work well.
I end with a top knot or an I-cord or a pom-pom. It's easy to experiment here because these hats are so small.
The weather has been a bit cooler lately which makes it perfect for knitting. I'm working two days this week and I've gone in early to have some quiet time to work on these little hats.