Rag curls? Help!

Hi, I am having trouble using rag curlers in my hair! My mom used to do this to me when I was little, but I can't remember exactly how she did it. I have read several articles on the internet on this, but I am still having trouble, thought maybe someone here could help. I have mid-back length hair, that is very fine, and I have trouble keeping the hair and rag together when twisting, the hair wants to slip out. Also, when you get to the point of tying the ends of the rag together, since my hair is so long, do you roll it, or just tie a big knot? Any tips for keeping the ends of the hair in the knot? Anyone who has had luck with this, please help!! Thanks, Ellen