1. Teach them to LOVE books: Great readers make great writers. Kids (and adults!) tend to believe they are either readers or not, but I believe there is a reader inside everyone, they just need to find the right book! As a parent, you can help by reading aloud to them and helping them search for books they will love. It also helps when they see you spending time reading, so learning to become a reader yourself can help your child succeed!
2. Try Creative Writing: Even if you love to write, you probably don't want to write an essay about something you don't care about. So find fun things they are interested in to get them writing. If they are funny, have them write a comedy set and perform it for you. Grab or make some puppets and let them write a play. Challenge them to write a song. Let them focus on the right brain creative side without editing themselves. Don't worry about grammar or punctuation (yet), just create. It's what we're here to do!
3. Write with them: Try a guided parent and child journal, or simply get an empty notebook and write back and forth to each other. Bonus, rip out the pages and teach them to fold them like the cool notes we passed in middle school.
4. Get new pens and notebooks: It sounds simple, but there is something about a new, blank notebook and a nice pen that makes you want to sit down and write! Challenge them to fill the notebook with a mini story or comic book.
5. Try typing or dictation: Sometimes it's the act of writing that is difficult, not the creative process. Switch to typing a story if that helps, or better yet, have them dictate their ideas to you while you type. You can even try voice-to-text notes, although be warned that they may not know what they were trying to say if it gets the words wrong!