When you have to summarize a novel or story, think in terms of the main components of a story: characters, setting, conflict, plot, and theme.
Characters are the people who populate the story. You could summarize Hoot by saying that the main characters (protagonists) are Roy Eberhardt, a teenage boy who lives in Florida; Curly Brannit, a construction site foreman; and Officer Delinko, a patrolman in Coconut Cove. The antagonists (those who oppose the protagonists) for each of those characters are Dana Matherson, a bully; Chuck Muckle, the Vice President of Mother Paula's All-American Pancake House; and Mullet Fingers, a teenage runaway who interferes with construction at the Mother Paula's site.
The setting refers to the time and place. The story takes place in Coconut Cove, Florida, in the early 2000s.
The conflict of the story centers around what the main characters want and need. Roy wants to keep from being beaten up by Dana Matherson and to find out about the running boy; eventually he wants to help the running boy, Mullet Fingers, save the burrowing owls. Curly Brannit wants to clear the land for the new Mother Paula's pancake house and to remain employed. Officer Delinko wants to become a detective; he wants to impress his supervisors at the police department by arresting the perpetrator who is interfering with clearing the land for the new Mother Paula's restaurant.
The plot is closely related to the conflict; it follows the events of the story as the main characters pursue their goals or try to solve their problems. It culminates with a climax, or high point of the action, that sets up a resolution to the conflict. In Hoot, the plot revolves mostly around Mullet Fingers and his efforts to stop the clearing of the land. His continued escapades—pulling up survey markers, putting alligators in the portable latrines, spray-painting the windows of the police car, letting snakes loose on the property, removing the seats of the heavy equipment, and finally burying himself in an owl burrow—drive the action, pull Roy into the effort to save the owls, and cause problems for Curly and Officer Delinko. The climax occurs when Roy, Mullet Fingers, and Beatrice band together to stop the groundbreaking.
The theme refers to a universal truth a reader can draw from the story. There can be several themes in a work; just be sure you can support any theme you suggest with evidence from the story. In Hoot, one theme is that people, even young people, can bring positive change to their communities by getting involved and fighting against injustice.
You could pick any two of these story components to focus on in giving a summary of Hoot, but telling about a book's conflict, plot, and theme will provide the best overview of the work.