Learn a lot about the world and finish things, even if it is just a short story. Finish it before you start something else. Finish it before you start rewriting it. That's really important. It's to find out if you're going to be a writer or not, because that's one of the most important lessons. Most, maybe 90% of people, will start writing and never finish what they started. If you want to be a writer that's the hardest and most important lesson: Finish it. Then go back to fix it.