It's a pretty basic process - get/make some clay (I just used a block of Sculpey), press a paw in it, make a hole, bake it, and hang it on a string. I did learn a few tips though...
I found the Sculpey clay to be kind of hard and it was tough to get a deep print. I warmed it up in the microwave for about 20 seconds, and it worked much better. Smokey also like it much better (warm & smushy > room temp & stiff). Even after trying the microwave trick, it took me two tries - you can see the one on the left isn't very well defined.
I planned to make a kitty version too. It could just be me, but from my experience, kitty prints do not work. Aria's print just looked like a tiny, undefined blob. Not exactly tree material. I still wanted an ornament for her though, so I tried out my sculpting skills - elementary school art class style. I may not have a career as a professional sculptor in store, but it turned out better than I expected (plus it was fun to play with the clay!).
And lastly, you can't really tell from the pics, but this is silver clay with tiny sparkles in it. It looks great with the Christmas tree lights. When given the option, always go for sparkles.