I first showed my class a Mr Squiggle clip off Youtube (a show I remember watching as a kid and being fascinated with). I then put a blank squiggle on the board using, my eBeam. I got the class to offer ideas as to what they saw the squiggle as. We then jointly constructed a story together. They then got to complete one independently. They were very excited and couldn't wait to start.
I now use this activity as an independent writing task on a weekly basis. The handwriting lines are great for those kids still learning to form their letters correctly. I've made a booklet of my own which includes more lines for those better writers who are capable of writing more.
Sguiggle Stories Booklet has 20 lined pages with set squiggles, plus a blank squiggle page. Get from TPT: http://www.teacherspayteachers.com/Product/Squiggle-Stories-Book-801351