A Step-by-Step Tutorial
This tutorial not only shows you how to make plastic yarn, also known as plarn; but it also shows you how to make it into a more delicate thread-weight yarn. I have not worked much with plarn, but it isn’t the easiest to work with, I’ll tell you that. But this looks a lot more promising.
You might also enjoy more free crochet patterns and tutorials by Crochet is the Way.