What would be the appropriate clothes to take for both night and day for traveling to Ireland in Dec? Would waterproof shoes/boots be recommended?
Yes, and rain gear, umbrella, etc!
What is worn for night at the pubs? Is it mostly casual?
Yes, you should be okay casual--unlike continental Europe, they are almost as badly dressed as we are. :) (just kidding, please no flames). Lots of wool and tweed in December. Nice thing about wool in that climate is, even if it gets damp, wool (unlike cotton) does not lose its insulating ability. It won't smell very good, but hey, it's Ireland in December....
Layers, layers & more layers. The main thing in December is to keep dry. Even though the actual temperature is not as cold... as let see.. NY city in Dec.. the wind will cut thru you and make it seem colder. A waterproof jacket ... like Columbia w/a fleece lining would be perfect.
Pubs in Ireland are VERY casual & in the winter more so...