Be certain your main character has a worthy, noble goal — no one likes a shallow greedy protagonist.
Consider the tension of a ticking clock. Time limits for reaching a goal will create an urgency that readers find compelling.
A plot is one obstacle after another — never make it too easy for your protagonist.
Your main character needs to solve his own problems. Readers like active protagonists who do something, not passive kids who are done to.
Your main character must act consistent with the person you have created him to be. If a wimpy kid turns into a hero or a bully becomes compassionate, the reader must have sufficient reason to believe that can happen.
The protagonist’s goal must be important to him. Something must be at stake if he fails — something big. Look at your story and ask yourself, what happens if my protag fails? Are the consequences great enough to create strong motivation to overcome?
Jump into the story at a moment of excitement. Even the best conflict won’t help a story if your reader abandons you before he gets to the exciting part.
Resolution of the story must not leave reader with a lot of lose ends or questions. Readers expect to see the main character reach his goal, or abandon the goal in favor of a more desirable goal. Never give the reader the impression that you just got tired of the story and ended it — the ending should be emotionally satisfying and logically drawn from the characterization and story details.