I definitely agree with Mothbrad on this. Practice makes a good writer.

The more I write, the better I write. The more frequently I write, the more frequently I dream about my writing. The more frequently I dream about my writing, the more imaginative my writing becomes.

I look back at my earlier stories, and half of them feature protagonists who were a lot like me or who I wanted to be, even if my stories were fantasy and obviously nothing like Earth. I won't say that they were necessarily Mary Sues, because I greatly dislike that label - it tries to say too many conflicting things that leads only to confusion on the part of authors who are criticised for having one.

Someone once said that you have to write 300,000 bad words before you'll ever write something good, and I can say that after two successful NaNoWriMos and several novels I've started but not finished, I finally feel like I'm starting a story that actually has real potential. Not that the others couldn't become good with editing or that they were bad stories, but this one is different.

Oh yes, and good pens and reading a lot also help