My advice for young writers is to keep reading widely and for pleasure. And don't get discouraged! So much of it is just mule-like persistence. That's what I feel I learned this time around. There were many times when Swamplandia! failed and I had to pick it up and try and write it again. There were stories in my collection that were just duds, they've been voted off the island, and it was only because I had this material commitment to getting them out the door that I was willing to keep working at them. I really do think that's the best advice—to keep at it.
Someone told me this plumbing analogy once, "The water has to run brown for a while before it's clear." And I thought, uh no, if it's running brown maybe you should move! But that is kind of true, you have to become comfortable writing suckily for long stretches. That's the hard part for me anyway, thinking that there's no way, that the project is doomed, and continuing to push through that feeling. I've learned not to despair. Even when I'm writing pretty badly, I don't feel it's impossible that this could become something if I give it time.
And that's good advice too: it really does take time. I felt encouraged hearing George Saunders say that he spent a year on a short story once. That it was a dance of his conscious and unconscious mind before it came together and he had the right ending. He was just willing to be patient. There are some narrative problems that you can't just come at head on, they sort themselves out over time, you can't sit there and solve them.