Terra on the Bookshelf ran a beautifully thought out post on this subject. The addy to that wonderful post is here.
I would also like to add that if you do decide that your family can be expanded by another addition, did the homework to find out what would fit into your family, I still ask that you do not get a pet as a present. The house is usually at it most chaotic, often people travel that day, plus there are too many things that can present a danger to pets at this time (tinsel, packaging, wrapping, tree ornaments, chocolate, and so on). What would be better is to perhaps get the things that you need for the animal coming. We did that for my dad. We got him a crate, bowls, leashes, and as many necessities that we thought he would need before the little guy came to him. It was perfect. A promise of a new buddy but without the stressed out pup. If you need to get started in this area, then click the dobie on the left to enter the dog giveaway. ;)
I would also like to add if you are getting a dog at any time, don't forget the training. I am so big on training. Not just potty training, but training to get him to be a good citizen. I believe that if more people trained their dogs, it would have prevented many going to shelters. So, I will also add to the list of things to get a new dog is training. If you are looking for a general training book, I do suggest one like "It's Me or the Dog" (I put a copy of the book in my suggested widget on the left). She trains in the way I often advise. She also has a tv show so you can see her techniques up close.
The first video below gives a top 10 checklist before you adopt a pet by Victoria Stillwell.