The Rejector, a blogging literary agent, has some tough advice for young writers posted on his July 30th blog. His take is controversial - he doesn't think you can write well without experience and maturity behind you. But having said that, he gives some advice on how to improve your craft.
If you're a young writer interested in improving your craft (aren't we all?), join NaNoWriMo for a crash course in writing a book in a month. It's crazy fun, and I'll be trying it again this year. No fee, and you can sign up now and get email reminders before it starts in November.