If you want to be a good writer, you have to be a good reader. You may have even wanted to write because of the books you read and enjoyed; this happened to me after reading Harriet the Spy, but I digress.
I deeply regret that I did not discover Diana Wynne Jones until middle school, when I found a copy of Seeing is Believing in the library and picked it up for its title. When you have stories where a girl with mumps creates a story with a bloodthirsty heroine that comes to life, a writer who finds success after getting a computer (and the customary typos), and the story of a cat who helps a stupid magician's servant, you have no choice but to find the rest of the authors' books. I discovered A Charmed Life, Dogsbody, The Homeward Bounders, and proceeded to read every book by her in both the school and public library.
Diana Wynne Jones taught me that anything can be magical, whether it's the green flakes in a chemistry kit or a Friendly Cow. She also taught me Murphy's Law for fantasy novels: anything that can go wrong with magic will, and the disasters will make you laugh. Wizards do not always appreciate people cleaning their houses for that, and they are not necessarily elderly, well-behaved gentlemen; sometimes they are angry fathers pretending to be evil magicians. Heroes won't always know who's in trouble, or how to correct their spells; sometimes you might break your neck twice and still live. Use every implement that you introduce, since golden bricks may be useful to drop on the villain's toes.
Villains can be hidden in plain sight; your parents may not be the villains, but they are certainly no help when push comes to shove. Kids have to rely on their own magical objects and abilities, even if they didn't know that they have abilities. Don't underestimate a pit of orange juice or a cocoon of bookcases if your college roommate is targeted by assassins. Also don't underestimate the insults that brothers can exchange after one decides to attend university.
Most of all, there are no formulas to follow. Jones admired Tolkien's work, but she came to mock the sword and sorcery fantasy that succeeded Lord of the Rings; that fact made me admire her the most. For the record, I tried reading Lord of the Rings twice, and I learned that there is such a thing as too much description. Not all villains are pure evil, and you shouldn't have to travel alone. There is more than one way to solve a problem, especially if you are creative; there is no need to slay dragons with swords when a hot chili pepper will do.
Rest in peace, Diana, and thank you for your writing.