I adore Poinsettia, I don't have one this year as I'm not quite sure where I'm going to put it - I'm thinking maybe I'll buy two and arrange them either side of my beauty advent calendar which is so huge it'll look fabulous with these wonderful red plants as a backdrop.
Poinsettia's are the Christmas plant, I know nothing about growing them as the ones you can buy at the garden centre or supermarket are excellent plants to see you through the festive period. There is a way through trimming of keeping your Poinsettia for next year but I don't have the room to store clipped-back plants so tend to compost the plant when it's died off completely, once I planted three in the garden and they survived for ages - I wasn't expecting them to and have since been told that transplanting a Poinsettia to the garden is really tricky so I must have just got lucky as I didn't do anything special (dug a hole and popped the plant in!).
The sap in a Poinsettia plant can be poisonous to dogs but a vet told me that although the risk is there not many dogs are a) affected or b) interested enough in the plant to eat it. If your dog or cat does ingest Poinsettia sap they'll be sick and uncomfortable so that's good enough reason to not really have this plant if your pet is inquisitive - we have a Jack Russell so have plenty of 'higher than Jake' places to put the plant, although to be honest there's only been one year when we've foregone the Poinsettia due to a dog and that was when we had literally nowhere to put it out of reach and the dog we were looking after liked to eat plants.
In terms of keeping your Poinsettia alive I don't know what the official instructions are but I tend to lightly water it every day and once a week give it extra water followed a couple of days later with a plant food. This seems to work for me and our Poinsettia's look great well into January, I have a thing about Poinsettia that as long as it gets me until New Years Eve I'm happy and these days they mostly do - I don't keep the plant until every shred of prettiness has dropped off and do waste a few days by composting earlier than is necessary sometimes, but as much as I love this beautiful plant I do feel it starts to outstay its welcome once the Christmas decorations are down and definitely consider it to be a festive-time only plant.