Hi john,
I water mine when the compost starts to feel dry to the touch. I put the water in the bottom of the saucer and let it soak in. excess water gets tipped out after about 1-2hrs. Sometimes I let them get to the slightly wilting phase [not deliberately]and they rapidly recover. keep them out of draughts though.

I think the biggest problem with poinsettia plants is not the watering but the over heated homes they have to live in. I once kept a poinsettia until June because it was in a cool room. I realise this is not practical for most of us.