I've seen mature bucks lose their antlers in December also. I think the dominant bucks that are doing the breeding often lose their antlers first, to help them survive the winter when the breeding is over. It is usually precipitated by a drop in testosterone after the rut.

As far as looking for sheds, feeding places and bedding areas are the best. It can happen amywhere however, so keep your eyes peeled at all times. It will be difficult to find them in the deep snow, so most guys go Late March, early april. Like the other poster said, the more you're out there, the better your chances, plus you get to learn the lay of the land and how they're using it