Goodgulf:
Complete physical descriptions of everything.
Detailed descriptions can make a setting memorable and can also add a lot to a story. The kind of writing that I enjoy the most would probably be greatly diminished without it.
That said, it is very easy for a writer to go overboard. The later books in Jean M. Auel's
Earth's Children series (that's the one that begins with
Clan Of The Cave Bear ) really dragged for me because of that. Just because a couple of people are making a very long journey across prehistoric Europe, that doesn't mean the readers need a detailed description of every bird, plant and rock along the way.
The worst example I've ever come across though was in James Michener's
Centennial . The book is mainly about the founding and growth of a town in the old West. It follows the story through several generations and like many of his works was a best-seller. Here's what had me groaning though. The author devoted the first fifty pages to describing the geological forces that shaped the land where the town was eventually founded. The pushing of tectonic plates caused this part to be higher than the rest, volcanic activity 50 million years ago gave this hill its current shape, the erosion of the this river carved the valley below over a period of hundreds of thousands of years, etc., etc., etc. I kid you not. Fifty pages!

That was way, way, WAY too much background for me.