Develop your main idea for your paper. Delve more deeply into it than just the subject. If you are writing about a specific book, for example, think about the main point you are trying to make. Choose a fiction or fantasy story, such as The Golden Compass, and make one point, such as that the Golden Compass follows the traditional "fantasy" genre.
Decide on a main argument you want to make with your paper. An argument doesn't have to be one side or another, it can be a simple statement that you want to prove. An example might be "The Golden Compass follows the traditional fantasy genre's pattern of writing."
Decide which examples or facts you are going to use to promote your main idea. These will make up the majority of your paper, but should be in your thesis statement. For example, after adding these in, your thesis statement might read "The Golden Compass follows the traditional fantasy genre in that it is a fantastical story of a young heroine who travels through different worlds."
Add in an element that finishes off the point you are making, or anything that is proved by your examples. For instance, your finished thesis statement might read "The Golden Compass follows traditional fantasy genre writing by providing the story of a heroine who travels through different worlds to, in essence, save those worlds."