I was frustrated with my writing, like I was hitting a brick wall so I'm back in school. I just took a class that challenged what I thought I knew about writing.
1. Notice your writing process. Do you need a schedule or do ideas happen randomly?
2. Life is rich with inspiration for writing. Use your senses to take in and process the world around you. Listen to how people talk, what they talk about, and what they avoid talking about. Watch the news or read newspapers. List the things you would never write about. Then list the things you'd be slow to write about. Give a brief reason for not writing about those things. Maybe that will open the door for you to write about these things or somehow include them in a character's life. Take an issue you feel strongly about and write it from a different perspective, perhaps the extreme opposite perspective.
3. Pick a genre you thought you'd never use, such as creative nonfiction, literary, mainstream, religious, or sci fi.
4. "Show, don't tell." Where you explain too much (exposition), reword it, adding sensory details so the reader can "see" your story and leave some details to the reader's imagination (in-scene) for the same reason.
Making it flow can be tricky. One part of your brain is creative and the other logical. The creative side allows you to run with an idea and allows the story to write itself. The logical side wants to steer you a particular direction, criticize you, and point out grammar and spelling mistakes. Acknowledge the logical side and its criticisms, and keep writing. Play with your writing and freewrite then go back and take the sentence that has the most feeling and power and run with that. See where the story leads you. Nothing you write is set in stone. Even if you wrote something you absolutely love, it might not fit the story. That's ok. Save those ideas in a separate document and follow where the story leads.
Make sure you have fun writing. If you don't, your readers might not like it either.