I used a 5mm hook but you could use any size just by increasing or decreasing the length if the starting chain.
Ch20 (or more if you want a wider scarf)
Row 1 hdc in each ch across, ch2 turn
Row 2 hdc in each hdc across, ch2 turn
repeat row 2 until the scarf is the desired length i made mine 39 inches for a 4 year old boy. DO NOT fasten off
To finish off sc in each chain all the way around the ends and sides of the scarf (sc ch1 sc in each corner) this just evens out the edges a bit.
Finally add tassles. Here is a video which explains how to do this if you have not done it before VIDEO