All the craft books and lectures and newsletters in the world won’t help you get around the cold hard fact that if you are a writer, and you are looking to improve your work, the only real way to do so is to write more. What you practice is what you get good at, and while your initial attempts at writing won’t be anything special, eventually you will have produced enough material that the aspects of it that gave you trouble at the outset become automatic, and you can spend your time and energy on pushing the quality of your language and ideas to higher levels.

Writing more—even/especially if it’s bad—is also the one sure way to get over writer's block. Dan Harmon says:

Switch from team “I will one day write something good” to team “I have no choice but to write a piece of shit” and then take off your “bad writer” hat and replace it with a “petty critic” hat and go to town on that poor hack’s draft and that’s your second draft.

Ira Glass says:

The most important possible thing you can do is do a lot of work — do a huge volume of work. Put yourself on a deadline so that every week, or every month, you know you’re going to finish one story. Because it’s only by actually going through a volume of work that you are actually going to catch up and close that gap. And the work you’re making will be as good as your ambitions. It takes a while, it’s gonna take you a while — it’s normal to take a while.

Scott Young says:

One hundred essays is probably a good benchmark to hit before worrying about whether what you’re writing is good or not. Again, if that sounds like a lot, it is! Writing one hundred essays is probably a year’s worth of work. But it’s a year that will tell you what kind of writer you are and give you a starting point for trying to improve.