Found a great quote yesterday: The dignity of an iceberg is due to only 1/8 of it being above water. A good writer does not need to reveal every detail of a character or action. ~Ernest Hemingway
I love that "iceberg" idea - the notion that we don't have to "write" the entire iceberg. That if we just reveal 1/8 of it, the reader will "get" that there's another 7/8 below the surface.
This is where we have to treat the reader as intelligent. We need to assume that the reader will read between the lines, will think for himself/herself, will "get it." I've mentioned before that I have a tendency to over-explain in my writing (the hazards of the job of teaching, I suppose). I'm constantly having to remind myself that if I write the 1/8th of that iceberg well enough, the readers will then see the rest of it on their own.
Now, of course, Hemingway was well-known for VERY sparse description. In fact, for me, it's often too sparse. But he is right, about not revealing too much. It's unnecessary to do so, and it will probably bore the reader. Better to reveal too little than too much, I think...