One of the best ways of learning the writer's craft is to read. Surprisingly, many aspiring writers don't realise this. Oh, they read, but it's usually "how to" books about writing, or Writer's Digest, or Writer's Market, or Strunk & White. Those are all helpful works and invaluable for learning the tools and skills of the trade, but I'm amazed at how many writers don't read more general works–particularly the sort of works that they hope to emulate. It's like learning to paint by reading up on painting, but never looking at a work by Leonardo da Vinci or learning to sculpt without glancing at what Michelangelo turned out. Come to think of it, having visited the Tate Gallery, I'd say that painters and sculptors have the same problem.
Reading to write fulfills a number of purposes.
First, a writer must always be learning new things. A day shouldn't go by when you don't discover something new like the atomic weight of boron or what the 39 Steps are. All these facts, observations and insights are grist for the mill–as are clichés so be avoided, such as "grist for the mill".
Second, reading provides concrete examples of how to write and how not to write. Learn from the strengths and failures of other writers. Go to P G Wodehouse to learn relentlessly logical plotting and the perfect simile. Look at Tolkien to learn how to create back story. Ian Fleming tells you how to polish an opening paragraph. Tom Sharpe provides tips on writing farce. And the immortal E M Forster shows you exactly how not to use a comma. If you're learning how to master a genre, then read in that genre. If you want to learn the style of particular author, then read that author.
Reading is also an excellent way of staying focused on the task at hand. I ceased being a real fan of science fiction years ago, but when I started work on Tales of Future Past, I had to revisit a lot of old sci-fi as research and I read little else for relaxation for over three years because I found that it kept me in the right frame of mind for my work.
Of course, it isn't enough to just read. You need to read with the eye of a writer. Don't just skim over the opening sentence of a new book; study it. See how it captures the reader's attention; look at what it reveals. As you go along, pay attention to the structure of the chapters, the cadence of the sentences and the use of metaphors and similes. Make a note of how the author foreshadows the action, how characters are introduced; what is said about them and what is left to the reader's imagination. One exercise that I've found useful is to keep a chart of the story line with dips and valleys on a graph representing the triumphs and setbacks of the hero (I'll revisit this topic in more detail later).
Finally, cast a critical eye over the work. What does the author do right? What are his shortcomings? Is a character wasted? What sort of plot holes are there? How much are you expected to suspend disbelief?
Even if you're writing non-fiction, the advice still applies. In fact, writing feature articles, news reports, and such like often requires a much more rigid format that only careful study will help you to truly master.
Besides, reading is great fun and any excuse to do so is a good one.