Writer's Fallout Shelter

Good question. I wish I had a good answer.

What details are important to your story? What ones are necessary to capture your reader's imaginations and permit them to visualize the characters? Is it important for them to see the characters exactly as you see them or can you allow their imaginations to work for you? When is it important for your readers to know the information?

The answers to those questions can help guide you, but the truth is, what works for one story won't necessarily work for another.