Following from yesterday's post, I feel compelled to further discuss layout and design. Every single writer should know basic layout and design. It is an entire set of skills that are easily overlooked or ignored, but which can make a massive impact on how your writing is received.
For the sake of defining my terms, I consider "layout" to be formatting text to attain a desired visual aesthetic, and "design" is the creation of nontextual visual elements. I usually put the two terms back to back because they go hand-in-hand.
I have mentioned before that there are a great many aspects to writing which people are not conscious of, but which they are unconsciously affected by. Layout and design are two of those aspects. Every time you end a paragraph with one or two words on the last line, or your last page only has two or three lines on it, or you have a paragraph where one line happens to stick out further than the other, you are bothering your readers. It is a visually ugly thing. By the same token, if you ever put yellow text on a white background, or bright red text on a bright green background (God help you), then nobody even cares what your words say because their very existence is offensive to the senses.
Learn your shapes and your colors. Right angles are strong and formal. Straight lines (including invisible margins) are clean and attractive. It is better to put darker text on lighter backgrounds than vice versa. Learn what complementary colors are and never lay them on top of each other.
I am not saying that you need to become a professional designer. I am saying that you need to know the absolute basics. You need to be able to make documents that don't suck. You should be able to make documents that look attractive, even if people might say that they look like a first-year design student. That is a thousand times better than being told that it looks like a fifth grader laid it out (or that it was a fifth-grader's cat).
Being a great writer is valuable. Being a great writer who can also lay out and design a decent document is invaluable.