On this account, I'll probably only be writing short stories.
I want to mention some tips for writing:
When you're writing stories for kids, try to write short chapters. Long chapters, even as an adult reader, can get you down. Short bites give you a sense of accomplishment, a feeling of moving forward.
Write every day. Even 5-10 minutes will make you a better writer, and improve your stories.
In many of my stories (Most of which I haven't posted) I incorporate some of the real world, something that happened to me. People often want a feeling of familiarity. I take an event from my life, and twist it and turn it and add bits of fiction everywhere. It's a good way to start writing or get an idea.
For the first time you write your story, it doesn't have to be perfect. Just get it down, then go over it; be prepared to rewrite and rewrite and rewrite 5, 6, 7 times.
In short stories, keep it simple. Don't try to stuff a whole, big, huge chunky novel into 500-1000 words.
Get a writing book or Notebook out. Now write, whatever you like, 5-10 minutes straight. Your pen is not allowed to leave the page. Do this every day. It will hugely improve your skill as a writer.
Read! If you read a lot, more often than not, you will find yourself a talented writer. Adults and teens are often claiming to be too busy to read. Just take a moment, every day, to have at least a small 5-10 minute read. Don't force yourself. Sometimes, you just need to find the right book, and then you're off!
Here are some amazing ones:
The Hunger Games (Suzanne Collins)
The Bridge to Terabithia (Katherine Patterson)
The 'Once' series, including: Once, Then, Now, After, and Soon (Morris Gleitzman)
The Honest Truth. (Dan Gemeinhart)
Grimsdon and New City. (Deborah Abela)
Thanks for reading!