A few suggestions for aspiring writers of all ages

Read – From Stephen King: “You have to read widely, constantly refining (and redefining) your own work as you do so. If you don’t have time to read, you don’t have the time (or the tools) to write.”
Revise, revise, revise. Your first draft is just that: a draft. Even great writers never get it right the first time. Don’t be discouraged. Keep writing.
Ask for help. Ask the right people, that is. People who know more than you about what it is you want or need to know. Most people are glad to help when asked.
Get feedback. Friends, acquaintances, other writers, people you trust. Preferably people who love books. You want honest feedback. You need honest feedback. Take feedback seriously. Don’t be offended. It can be hard to hear, I know. Don’t get defensive. Fix what needs to be fixed and move forward.
There’s a wise saying among writers attributed to several sources that goes something like this: “Don’t be afraid to kill your darlings.” Don’t be afraid to press the delete key. Honest, sometimes that’s the best solution. Keep writing.
If you can afford it, hire professionals. I used UK-based Reedsy.com to find and hire editors. It is free to join. They also have tons of free resources for writers of every genre. If you are looking for an editor (developmental, copy, proofreading, etc.), you can browse their vetted list of freelance professionals and request bids from up to five of them on your project. You pick who you want to work with. I had several wonderful and supportive editors. You can also find cover designers, layout folks, illustrators, and marketing experts. I highly recommend this fantastic service.
Find a local or online writer’s group. Here are some ways to find them. Here is a list of online writing communities.
If you are interested in writing for MG or YA read this book: How to Write Irresistible KidLit by Mary Kole. It is one of the most helpful and practical books on writing I’ve ever read.