Well, I always start here, with this reminder: http://zenpencils.com/comic/90-ira-glass-advice-for-beginners/
Next... start throwing your writing to the wolves, hard. This takes time and work. Seek out critique. Seek out *tough* critique. Reciprocate it when asked. There are critique circles out there if you look, but you must look.
You must seek.
And you must love your words enough to throw them to those wolves and say "Kill those wolves. Slay them. Or come back with scars that make you stronger."
I've been writing professionally for a long time. First publishing contract in high school. I was terrible then. I was terrible a year ago. I was terrible yesterday.
But I fail better, every time. I don't worry about success, I worry about making sure that I learn from my current failure, my next failure, and my next.
I want to fail and keep on failing until I fail so well other people can never tell it from success. I want to (and have) fail so hard and well that *I* can't tell it from success. (At least until six months down the road, when I see how I could have failed better.)
Over and over again, I seek that. I am always learning, always seeking out tough critique, always looking not for the people who'll just pat me on the head and say "Good job!" but the people who frown thoughtfully and say: "Hm. What about this, over here?"
I LOVE THOSE PEOPLE.
I tell fellow writers, that I try to keep a stable of feral and savage beta readers. People unafraid to tell you when you suck, but also willing to put in the time to tell you *how* you sucked. It's from them that I learn. It's from them that I get better.
In closing: Take the training wheels off, get your knees and ego scraped and bumped. And keep throwing your words to the wolves until they're badass motherfucking wolf-slayers.
(THEN throw them to the dragons.)