These are cherry-picked from a Pixar storyboard artist, Emma Coats:
1. Coincidences to get characters into trouble are great; coincidences to get them out of it are cheating.
2. Trying for theme is important, but you won't see what the story is actually about til you're at the end of it.
3. You gotta keep in mind what's interesting to you as an audience, not what's fun to do as a writer. They can be v. different.
4. Come up with your ending before you figure out your middle.
5. What is your character good at, comfortable with? Throw the polar opposite at them. Challenge them. How do they deal?
6. What are the stakes? Give us reason to root for the character. What happens if they don't succeed? Stack the odds against.
7. Give your characters opinions. Passive/malleable might seem likable to you as you write, but it's poison to the audience.