To make doll hair for a knitted doll, you need to cut lengths of yarn that are twice as long as you want the finished hair to be, plus maybe an inch and a half more, to allow for the knot and a final trim - it's always better to make hair too long, so you can trim to the exact style you want, rather than hair too short, which doesn't look right.

Insert a crochet hook into the doll's head where you would like a strand of hair to be.

Fold one of your strands of yarn in half and put it on the crochet hook...

...then pull a loop through.

Take the two ends of the yarn and pull them through the loop you have just created...

Take the two ends of the yarn and pull them through the loop you have just created...

Then pull gently to create a firm knot. Voila - your first two strands of hair. Repeat all over the doll's head. This method gives you great control over your doll's hairstyle! Try using a mixture of different yarns and different thickness.

And here is the finished result, enjoying a cup of tea with Lucius Malfoy - you can buy both dolls and patterns in my Etsy shop.