Many will tell you to read more than you write, but I won't, because I don't. I do not feel reading is essential to writing. I do think it helps but it is not essential. What is essential is imagination.
Research. If like me you use myth and legend, go to the trouble of looking up all of the variables.
Get people to read your work and encourage them to be brutally honest with you.
If you are unsure of style, a writing course can be helpful.
Develop a thick skin.
Join a writer's community like Litopia and share experiences, gain advice and learn with others who will support and encourage you.
Most of all, have fun and don't give up. Writing is hard work but it's so, so worth it.