Read @Fanfic's guide to writing fanfiction. (Link in the external link.)
Enter contests to test your writing skills (like May The Words Be In Your Favour maybe? Check my profile.)
Once you have a complete novel, get a few beta readers to tell you what you're missing out on.
Try to explore multiple genres. Example: if you're writing just about romance, it's going to get boring. Tap some action, or adventure, or humour.
If you're writing a really dramatic scene, you can add music to the background for when readers read the intense parts.
YOU ARE READING
Tips For Writing Fanfiction
RandomExactly what the title says. (If you have questions, you can PM me. I'll try to help. Or, you know, take any insults you want to throw at me.)