Long scarves are often a bit of a nuisance, having too much bulk or length and with tails that get in the way. They also take a long time to knit, whereas a neck warmer is a quick-to-knit project that fits snugly around the neck and tucks neatly inside a coat collar. A basic pattern can be customized to fit any size, including adults and children, and is suitable for both men and women.
Cast on 21 stitches.
Knitting in seed stitch (K1, P1 every row) continue until the knitting is long enough to fit comfortably around your neck.
Cast off loosely.
You can either leave the neck warmer without fastenings to just wrap snugly around your neck, or you can sew on a couple of buttons. The seed stitch pattern should be loose enough for the buttons to just slide through the stitches so you don't need to knit buttonholes.
A second alternative is to knit the neck warmer a little longer until it is long enough to slip over your head, then sew the two ends together so you have a knitted tube.
Cast on more or less stitches to make the neck warmer either narrower or wider.
The seed stitch pattern assumes you start with an odd number of stitches. For an even number of stitches you need to alternate the knitting order of the stitches. The first row will be K1, P1; the second row will be P1, K1.