Use a famous book or story. Pick out an interesting novel or short story with a gripping opening paragraph which captures your attention and read it to the kids. Ask them what this paragraph which really pushes them to go on reading, is about. Inform them of the term "hook" and what it means to get the readers hooked.
Discuss literary techniques with the children. Give the pupils a list of various techniques that writers use to create an interesting introduction. These might include dialogue, a vivid description, or an intriguing fact. Ask them to try and identify where the "hook" is in the paragraph you have given them, and which technique it is that the writer has used.
Give the kids a narrative prompt. Every pupil should decide on a technique to keep the reader hooked, and then proceed in writing an introduction to a narrative based on the prompt that you gave them. Allow each of them to highlight the hook, and make note of the introduction's key terms.
Organize the class into small groups. Every pupil should take their turn in reading their introduction aloud. Have members of every group point out the hook and techniques used in every introduction. You may wish to increase the number of prompts used, to vary the use of techniques.