We often learn best by example so as writers what better way to learn how to write than by reading?
Choosing well-written novels and stories and analyzing as you go can help you to improve your own writing. Pay attention to the point-of-view and how the writer developes it; to the setting and the effect it has on the story; to the use of imagery and description; to how dialogue is written and what information is revealed through it; to how emotion is portrayed; to how background information is woven into the story; and to what method the writer uses to tell the story.
Keep track, even in writing, of things that stand out. It's especially easy to jot down images and descriptions. I saved this line from "The Bride from the Village of Deaf-Mute" by Brigid Pasulka: "He took Sasha's hand in his, and it shook like a baby bird fallen from a nest." I read that story for the first time a few years ago and it still randomly comes to mind. That is a writer I can learn from.
Are you working on a certain aspect of your writing? Seek out literature that does it well. Do you write in a specific genre? Find the masters in that genre and learn from what they've written. Then, go to work practicing what you've figured out.
For example, in historical fiction it's challenging to weave in details about real people or events without it turning into an exposition fest. So while reading Innocent Traitor by Alison Weir, I'm paying attention to how she does it. This story involves some complex political situations so I'm getting a lot of tips on how to handle it.
Most importantly, read as much as possible. Expose yourself to the many ways writers interpret their craft. Learn the rules of writing and see how they're broken effectively. Mimic the masters to get a grip on how to apply certain techniques. In the end, you'll see your own writing improve just by imitating some good examples.
Get Reading and Writing!
Choose one thing you'd like to work on in your writing. For instance, dialogue. Search for writers (or specific pieces) that excel in this area. The dialogue in Ernest Hemingway's "A Clean, Well-Lighted Place" and Julia Glassman's "Tenses" are good places to start. Think about why the dialogue is great. Why does is flow so well? Why does it make such an impact? Why do their words convey so much emotion? Spend some time analyzing your choices, picking them apart to get to the techniques behind them.
After you've learned a little something about good dialogue, apply it. Rework an old story using the new techniques. Or start afresh with the aim of putting your newfound knowledge to work. Your goal: For one, use your reading skills to learn on your own what makes good writing. Second, turn that new understanding into a skill you possess as well.