If you haven't knitted for a while and can't quite remember how to do it, this video shows you how to knit a rib scarf. 

You will need to have cast on already (have a look here if you need help with this) and I'd recommend casting on a multiple of 4 stitches so that you can start every row with 2 knit stitches (helps cut down the mistakes!).

Before you know where you are, you'll be back knitting again!