I'm not as good as some of the other people here, but one thing I do with Jacks and Arth when posing them for Christmas pics is -
1. When you take the pic in the house, use your finger or a treat to keep them from looking directly at the camera while also getting the face forward shot. Especially if you are posing in front of the tree and you've turned the lights down low to capture the Christmas lights.
That should be all you need if you have a very nice camera.
<- This pic was taken with my cheap point-shoot camera, and unfortunately even with my pointing a finger to the side and getting the dogs to look that way, I still got the little orphan annie eyes...
<- This was taken in heavy shade with the same camera, but the lighting was better as far as preventing eyeflash.
2. If one or two of your dogs know stay - USE IT. And train a good 10 second wait for the other dog.
3. Do not try to take the perfect picture. I take about 50+ pics and delete over half of them when I'm done.
4. If you want a natural pic (the dogs not sitting or laying there) get used to sitting outside and waiting with the camera cued up and ready.
5. And I agree about thinking ahead about the setting and what brings out your dog's colors, what would wash out or block your dogs, and what you do not want to have to clean up later on with photoshop.
<- That above pic with the three boys had to have an open bathroom cropped out on the one side and a garbage bag cropped on the other.
6. Look at your pics between shots to see what came out right for one dog and see what you can adjust?
^ With this picture I loved how Arthie came out because the lighting and pose worked for him, but wasn't crazy about how I set Jacks up.