You write about the obvious. Simple? Yes and no. So many times some of us writers tend to overlook the most obvious points we are writing about because we are so familiar with the subject matter. Surely, we thing ...wrongly it turns out... everybody knows this or that tidbit of obvious information. Naturally, I don't have to cover that ground! And then we're stuck. Or worse, we gnash our teeth when some other writer boldly states those obvious facts, figures, stories, etc. and receives accolades for them! Then we seethe and pound our foreheads against the keyboards and wonder why we didn't think of that.
Here's an example. I've written numerous books on antiques and collectibles, along with this children's book that inspired the creation of this infrequently visited blog (thanks for stopping by actually), and I had written four books on one particular nineteenth century ceramics line. I felt I'd covered it pretty well and was done with the subject. Then the publisher came to me and asked if I had leftover images from the four volumes. I told him I did and he suggested I write a pocket guide to the subject. Since the publisher is also my boss, I agreed. Then I was stumped. After four volumes, what was left to write about? Sweat began to bead my brows and slick my palms, until I had that oh so simple inspiration, state the obvious. Define the basic terms for the newcomer to the field. Identify the different dish forms used (the average Victorian dinner set had 101 pieces so there was plenty to work with). When I was done, I'd covered all the most basic of basic information. That little pocket guide sold quickly and well.
Never overlook the obvious. It always makes a solid foundation for an article or a book and many people really won't know the information you have, in your research, written off as too obvious for words.