Write a lot. I spent the entire 90s writing bad fiction. 5 bad novels. Dozens of bad stories. But I learned to handle massive rejection. And how to put two words together. In my head, I won the Pulitzer Prize. But in my hand, over 100 rejection letters.
Read a lot. You can’t write without first reading. A lot. When I was writing five bad novels in a row, I would read all day long whenever I wasn’t writing (I had a job as a programmer, which I would do for about five minutes a day because my programs all worked and I just had to “maintain” them). I read everything I could get my hands on.
Read before you write. Before I write every day, I spend 30-60 minutes reading high quality short stories, poetry, or essays. Books by Denis Johnson, Miranda July, David Foster Wallace, Ariel Leve, William Vollmann, Raymond Carver, etc. All the writers are in the top 1/1000 of 1% of writers. It has to be at that level, or else it won’t lift up your writing at all.
Coffee. I go through three cups at least before I even begin to write. No coffee, no creativity.