I like to have matching knitted accessories. I don't usually make something without something else to go with it, so when I was picking out Kureyon for my Camp Out Mittens (designed by Tante Ehm), I decided to grab a second skein so I'd have a hat to go with it.
Here's how I did it:
K 116 rows in garter stitch (or as many as you need to make the band long enough to snugly fit around your head)
BO 9 stitches, turn work.
Pick up 99 stitches along side edge of garter stitch band.
Place marker and join to knit in the round.
Knit until you have about 5-10 yards left.
Decrease round #1: K2tog around (50 st)
Decrease round #2: K
Decrease round #3: K2tog around (25 st)
Decrease round #4: K
Decrease round #5: K2tog to last stitch, K1 (13 st.)
Use tail from cast-on to sew garter band together.