My definition of a hook is a plot device that causes the reader to continue reading a story, usually in the form of an implied question. In turn the hook should raise the reader's curiosity and make them ask the question--"What happens next?"
Normally, there are certain places I expect to place hooks in my own writing. The start of a novel or short story and the end of each chapter. But after thinking about some comments from these posts I now realize hooks can be placed anywhere in a story to keep the reader reading, but there are four strategic locations to consider putting these valuable devices.
INTRODUCTORY HOOK (optional): The introductory hook is found at the very start of a novel or short story. It has two important things to accomplish. Get the reader to read further into the story. Get the reader to buy the story.
The intent of the introductory hook is to give the author time to establish the NOVEL/SHORT STORY HOOK. It is not a major hook in the fact that after the novel/short story hook is introduced its question may no longer be important.
Use an introductory hook when it's too early to answer the question of what the novel is about, but you need something to keep the reader turning the pages. It could be something as simple as conflict between two characters, the introduction of a strange event, or the description of a mysterious setting that the reader will want to explore.
NOVEL/SHORT STORY HOOK ( the main hook ): The novel or short story hook will appear very close to the beginning of the story. The shorter the length of the tale being told, the closer this hook needs to be to the beginning. If the story does not have an introductory hook, this will be the first hook they encounter.
The novel/short story hook acts as the bookend question to the story. It is the question that will be the basis of the book, story, or series. Once this question is answered the story will then move into the denouement.
Some examples from movies/books of the main hook:
STAR WARS--will Luke become a great jedi?
A FEW GOOD MEN--will they uncover the culprits behind the soldiers death?
A GAME OF THRONES--will the land survive the long night?
CHAPTER OPENING HOOK: The chapter opening hook is to get the reader to read to the end of the chapter. If it answers a question from the previous chapter, then it needs to either create a new question that the reader needs an answer to or it needs to build on the Novel/short story hook. It can be used to provide an elevating of the forces against the protagonist or it can be used to bring in a scene in which the character thinks/recovers from their trials.
CHAPTER ENDING/ CLIFF HANGER HOOK: This hook is the hook that causes people to stay up late into the night. Unlike the chapter opening hook which may lead to a rest period for the character, the chapter ending hook should create more tension and indicate that the character is not safe and still has more to do on their journey.
If you want to write a story where the reader is dying to know what happens next; give them a question that they want to know the answer to. Then you can get up from the table, go to dinner, the movies, or shopping. When you get back, the fish will still be attached to the line. Because you can't catch a fish without a hook.