1) Adults represent some of the most important relationships in a child’s life. Craft them with as much care as you do your young characters, and your readers will thank you.
2) Adults are people, too. Give them some good characteristics to go along with their faults and vice versa.
3) Adults can make mistakes, but they shouldn’t act stupidly. They need plausible reasons for the mistakes they make. And kids need to be very clever to outsmart them.
4) Adults need character arcs, too. What do your adults learn through the action of the story? How are they changed for better or worse?
5) Adults can be helpful and supportive.
6) But adults cannot save the day. Your kid characters need to get out of their own messes, especially during the climax of your story.
7) Adults can get in your hero or heroines’ way and make it hard for them to achieve their goals. In fact, it’s fun for kids if most of the adults in the story present an obstacle for the hero or heroine to overcome instead of giving them a helping hand (and it can be really fun if an adult does both.)
8) Adults need reasons for the way they act and the things they say. Not all of these reasons need to make it into the story, but you should know them.
9) Adults can be important or even main characters in your story, but make sure you have at least one other child or young teen for your hero or heroine to interact with. Kids like to read about kids interacting with other kids.
10) Have fun creating adult characters your readers will love.