At this point, I've got a process down sortakinda; I do some planning on and world-building before I even think about writing a script. Having a roadmap when you're writing is essential, at least for me. If I don't have one, I tend to flounder around and end up with page upon page of superfluous material that has little bearing to the overall story that I'm trying to tell. Or maybe it does, but it's just superduper boring.
I find that getting out and simply spending time with other writers is one of the best ways to improve your craft. I attend a monthly workshop at my local comic/coffee store, Legend Comics and Coffee (in Omaha, NE), and it's probably the best thing I've ever done for myself as a writer. I've met artists, other writers, and a wide variety of other talented people. Being in that environment give you a chance to discuss how you do what you with other people who are trying the exact same sorts of things.
And on top of all that nice stuff, I usually come away feeling far more inspired to write than I did when I stepped through the door. It's nice to have a group of people who care about what you're doing, and it's a good way to hold yourself accountable to actually produce something over the course of a month (which seems like it should be easy, but I have failed at it too many times to count).
So go, get out there and be a part of your local artistic community. It's one of the best, most rewarding experiences that you can have as an artist. And it's crazy fun.