All the above. And lots of reading, from Homer to Alice, and Edward Lear, and fairy tales and poetry, and Don Quixote and, and, - all the classics because they are the foundations underpinning the whole cannon including the moderns. And I tell everyone to get Fowler's Modern English Usage and read it cover to cover, and Roget's Thesaurus, and a really good dictionary (Webster's if you're American, otherwise Oxford - even the smaller editions will do to start). If you can get it, Olaf Ruhen's "Creative Writing" (the best I ever found on story construction, characterisation, etc). And Van Druten's book on playwriting which applies to novels etc too (pester your library!) And WRITE. Take a passage from, say, Joseph Conrad, read half of it, and try to finish it in the same style. Do the same with other great stylists, to get their music in your head. Write about the people, places, and events you know, and learn to make them interesting. A good story is more than a plot - most of all it is how the story is told. So don't overlook what is at your feet. The most "ordinary" lives are extraordinary when you've learned enough to see into them - and that comes from observation, experience, and time. Don't despair. Write for joy. You might also try drawing - it's the best way to learn how to see. It prints landscapes, scenes, gestures in your mind so you can recall them when required. Believe in and feel your characters and let them act out their story on their own stage. Get it down. Rewrite afterwards. Go for it!
A working writer's lifetime