Create characters that are quirky, imperfect and spirited. Include characters of any age but keep in mind that middle graders will care more about characters their own age or slightly older. Because readers should identify with and be the most concerned about your main character, this character should be around 12 years old.
Begin your story with a situation that causes a problem for the main character. Have her tackle the problem in a way that makes things worse. As long as readers care about your main character, they'll keep reading until she's okay.
Include plenty of trouble throughout your story. Problems, conflict and trouble fascinate readers. Never make anything easy for your main character.
Visualize the action scenes until you see them as clearly as a movie in your mind. Show what you've imagined through your main character's senses. Include what he sees, hears, smells, thinks or feels. Readers want to feel like the story is happening to them. Use your main character to give readers a first-hand viewpoint.
Give your readers plenty of surprises but play fair. If your main character escapes her enemy by climbing a tree, show her tree-climbing ability earlier in the story or have someone mention it. The unexpected turns in your plot will give middle graders a greater thrill if they can look back on the story and realize they should have seen it coming.
Include events that cause your main character to grow, change or learn something. This growth or new understanding should allow him to fix the main story problem in an unexpected but realistic way.
Allow your main character to solve the problem herself. Middle graders root for characters that fight for what they believe in and never give up.