It was kind of an accident for us; I bought a couple of cheap poinsettias at Christmas and a couple of branches fell down and came off as soon as we got home!
My mom put them in an old water bottle with some water and it looked nice in our kitchen. As time wore on, I was surprised when they didn't die. Finally, one of them just rooted! It's been more than three months. The other two still haven't.
But I think the one that rooted we got into the water right away compared to the others. I always kill cuttings when it's time to change the water, but she said to just add more, so that's what I did. Now, I need to figure out how deep to plant the one that rooted (I live in Florida)!