Write, write, write.
Edit, edit, edit.
Persist, persist, persist.
But target accurately. And study the publications you want to write for. There are no shortcuts. But this kind of research should be fun given you’re looking into areas where you want to write.
Keep your brain active by writing different things. It’ll exercise your writing muscles too. And it makes sure you are never short of something to work on. It can also buy you time. If you’re stuck on a novel, you can work on short stories and working on something else can help free the sticking point. I still don’t believe in writers’ block but I think it natural there’ll be days when the words flow beautifully and others when they don’t! We’re writers, not robots.
Outlining is well worth doing. It can save an enormous amount of time in that you work out the rough plot first and fill in the gaps as well as it stopping you going off on any kind of tangent given you have a kind of road map to help you write your story. I didn’t discover the joy of outlines immediately. Now I wouldn’t write a story without one.