There are loads of reasons why I love wearing my hair in a sock bun, not least because it's quick and easy when you have little time, the result being a tidy and stylish look. It's also really cheap - you don't want to spend upwards of five quid on one of those horrible doughnut things, which are always too big, especially if your hair is shorter than shoulder length.
You can find many videos on YouTube which show you how to do a sock bun, but the best one I have seen is by Tiffany on MakeUpByTiffanyD - which incidentally is a great website for loads of tutorials on make up. You can see Tiffany showing you how to do it here.
Before you get started, you'll need an old sock with the toes cut off, and the sock rolled down on itself. You can choose how big the bun will be depending on the thickness of the sock. If you want a bigger bun, use a thicker sock; if you have very long hair, or don't want the bun to be very big, use a thinner sock - or even one leg of a pair of tights (cut the tights above the toe seam and at mid-thigh, where the weave of the tights often gets thicker).
I've been styling my hair like this for some time. As I say, it's quick and easy, especially when you don't have a lot of time, or you haven't washed your hair. You can place the sock bun wherever you want: high on your head, or low down at the nape of your neck...even at one side for a more formal style.
It usually works best on two-day+ old hair...there seems to be more 'grip' when your hair isn't freshly washed. However, I discovered the other day that there *is* a benefit to using a sock bun when your hair is freshly washed - in fact, when it's still wet...ready made, easy curls!!
As you roll your hair around the sock, any natural curl your hair has becomes trapped in the sock; if you leave your hair to dry, when you remove the sock again, you will have lovely soft curls - disco! One word of caution though - don't tie the elastic for your ponytail too tight, otherwise you may end up with creases when you remove it...and no one wants that!