Over time, I've become a better writer. Here's what I've learned:
Keep reading craft books. In the past year, I've read at least a dozen. I put them on hold at the library two or three at a time. I'm far enough along now that I know if they don't speak to me. I recently read Techniques of the Selling Writer, an older book (you can tell it's older, because the author is Dwight V. Swain - when was the last time a kid was named Dwight?), and it was so useful! I found myself taking tons of notes on scenes and sequels.
Have a cheat book. This is especially true if you are writing for a living. You probably already have a book or two under contract. But you should have a book you are sneaking off to write every now and then. A book you are having an affair with. A book you are writing just for you! (Which may later end up being shared with the world).
Push yourself. Force yourself to work on a scene you don't want to for 15 minutes - after five or ten minutes you might strike gold. Or use any of the exercises in Writing the Breakout Novel Workbook (you don't have to have read the companion book for it to be useful). One I like goes something like this: "What is one thing your character would never, ever say? What is one thing your character would never, ever think? What is one thing your character would never, ever do? Find places in your manuscript where your character says, thinks and does these things."
Reading is also part of your job. Don't feel guilty about reading. I tended to put it off, thinking it was a "treat" that I only deserved if I had crossed everything off my to-do list. But then I read something from Amy Kathleen Ryan where she said that she considered reading part of her job. That changed my attitude.
Get Freedom, a program that cuts you off the Internet for the amount of time you set. You might think you are an adult and that you are able to control your own behavior. You are wrong. It costs 10 bucks, but it is definitely worth it.
These are the things that lead to great writing days for me. What tips do you have?