I think the most important thing you can do is make a conscious effort to improve. There's no single silver bullet, you have to keep looking for new sources of information, new experiences, and more practice.
And the second most important thing, think about what you're doing, why you're doing it, and how you can do it better. Same thing with previous projects. Look back at what you've done, and how you might do it differently now. Think about what could have been done better, or where you could still improve on it.
I see two great examples of this at work every day. I have one coworker who loves to learn, and wants to be the best developer he can. He's uses any downtime to read blogs, read books, discuss programming techniques, and ask tons of questions. He's also very noticeably improved in just the past year. Another coworker does his job, and does it fairly well. But that's all he does. He sticks with what he knows, doesn't make much effort to improve, doesn't work on any projects outside of his existing ones, and after 4 years, he has the exact same skill set and programming ability that he had when I met him.